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• How to force a new Notification in notify-osd to show up without waiting for the earlier one to exit?

  - by Nirmik

  I have made a script(and a .desktop shortcut leading to this script) for starting and stoping xampp... It checks the status of xampp and accordingly either starts or stops xampp. Now i have assigned a notification as soon as the script is started to display "Starting xampp..." or "Stopping xampp..." and then when xampp is started or stopped,it displays "Xampp started..." or "Xampp stopped..." I've used notify-send to show notification as seen in the script below Now the thing is that here,the second notification waits for the 1st one to disappear and then pops up even if xampp has started/stopped. I want the new notification to appear immediately by forcing the earlier one to exit before the completion of its life-cycle. This can be seen to take plce when you activate/deactivate wireless/networking immediately... For example the "Wireless enabled" comes up on selecting enable wireless and if you immediately select disable wireless,the "Wireless disabled" notification comes up without waiting for "Wireless enabled" notification to complete its life-cycle. So how do i achieve this? #!/bin/sh SERVICE='proftpd' if ps ax | grep -v grep | grep $SERVICE /dev/null then notify-send -i /opt/lampp/htdocs/xampp/img/logo-small.gif "Stopping XAMPP..." && gksudo /opt/lampp/lampp stop && notify-send -i /opt/lampp/htdocs/xampp/img/logo- small.gif "XAMPP Stoped." else notify-send -i /opt/lampp/htdocs/xampp/img/logo-small.gif "Starting XAMPP..." && gksudo /opt/lampp/lampp start && notify-send -i /opt/lampp/htdocs/xampp/img/logo-small.gif "XAMPP Started." fi On the man page for notify-send I found --urgency=LEVEL or -u where levels are low, normal, critical. Is this of any use? making it critical? Also I tried it with the command- notify-send -u=critical"Testing" but that dint work...it gives the error- Unknown urgency criticalTesting specified. Known urgency levels: low, normal, critical. or if I give the command notify-send -u=LOW"Testing" it gives me error missing argument to -u Any relation??

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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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• Are SQL Injection vulnerabilities in a PHP application acceptable if mod_security is enabled?

  - by Austin Smith

  I've been asked to audit a PHP application. No framework, no router, no model. Pure PHP. Few shared functions. HTML, CSS, and JS all mixed together. I've discovered numerous places where SQL injection would be easily possible. There are other problems with the application (XSS vulnerabilities, rampant inline CSS, code copy-pasted everywhere) but this is the biggest. Sometimes they escape inputs, not using a prepared query or even mysql_real_escape_string(), mind you, but using addslashes(). Often, though, their queries look exactly like this (pasted from their code but with columns and variable names changed): $user = mysql_query("select * from profile where profile_id='".$_REQUEST["profile_id"]."'"); The developers in question claimed that they were unable to hack their application. I tried, and found mod_security to be enabled, resulting in HTTP 406 for some obvious SQL injection attacks. I believe there to be sophisticated workarounds for mod_security, but I don't have time to chase them down. They claim that this is a "conceptual" matter and not a "practical" one since the application can't easily be hacked. Their internal auditor agreed that there were problems, but emphasized the conceptual nature of the issues. They also use this conceptual/practical argument to defend against inline CSS and JS, absence of code organization, XSS vulnerabilities, and massive amounts of repetition. My client (rightly so, perhaps) just wants this to go away so they can launch their product. The site works. You can log in, do what you need to do, and things are visibly functional, if slow. SQL Injection would indeed be hard to do, given mod_security. Further, their talk of "conceptual vs. practical" is rhetorically brilliant, considering that my client doesn't understand web application security. I worry that they've succeeded in making me sound like an angry puritan. In many ways, this is a problem of politics, not technology, but I am at a loss. As a developer, I want to tell them to toss the whole project and start over with a new team, but I face a strong defense from the team that built it and a client who really needs to ship their product. Is my position here too harsh? Even if they fix the SQL Injection and XSS problems can I ever endorse the release of an unmaintainable tangle of spaghetti code?

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• New Oracles VM RAC template with support for oracle vm 3 built-in

  - by wcoekaer

  The RAC team did it again (thanks Saar!) - another awesome set of Oracle VM templates published and uploaded to My Oracle Support. You can find the main page here. What's special about the latest version of DeployCluster is that it integrates tightly with Oracle VM 3 manager. It basically is an Oracle VM frontend that helps start VMs, pass arguments down automatically and there is absolutely no need to log into the Oracle VM servers or the guests. Once it completes, you have an entire Oracle RAC database setup ready to go. Here's a short summary of the steps : Set up an Oracle VM 3 server pool Download the Oracle VM RAC template from oracle.com Import the template into Oracle VM using Oracle VM Manager repository - import Create a public and private network in Oracle VM Manager in the network tab Configure the template with the right public and private virtual networks Create a set of shared disks (physical or virtual) to assign to the VMs you want to create (for ASM/at least 5) Clone a set of VMs from the template (as many RAC nodes as you plan to configure) With Oracle VM 3.1 you can clone with a number so one clone command for, say 8 VMs is easy. Assign the shared devices/disks to the cloned VMs Create a netconfig.ini file on your manager node or a client where you plan to run DeployCluster This little text file just contains the IP addresses, hostnames etc for your cluster. It is a very simple small textfile. Run deploycluster.py with the VM names as argument Done. At this point, the tool will connect to Oracle VM Manager, start the VMs and configure each one, Configure the OS (Oracle Linux) Configure the disks with ASM Configure the clusterware (CRS) Configure ASM Create database instances on each node. Now you are ready to log in, and use your x node database cluster. x No need to download various products from various websites, click on trial licenses for the OS, go to a Virtual Machine store with sample and test versions only - this is production ready and supported. Software. Complete. example netconfig.ini : # Node specific information NODE1=racnode1 NODE1VIP=racnode1-vip NODE1PRIV=racnode1-priv NODE1IP=192.168.1.2 NODE1VIPIP=192.168.1.22 NODE1PRIVIP=10.0.0.22 NODE2=racnode2 NODE2VIP=racnode2-vip NODE2PRIV=racnode2-priv NODE2IP=192.168.1.3 NODE2VIPIP=192.168.1.23 NODE2PRIVIP=10.0.0.23 # Common data PUBADAP=eth0 PUBMASK=255.255.255.0 PUBGW=192.168.1.1 PRIVADAP=eth1 PRIVMASK=255.255.255.0 RACCLUSTERNAME=raccluster DOMAINNAME=mydomain.com DNSIP= # Device used to transfer network information to second node # in interview mode NETCONFIG_DEV=/dev/xvdc # 11gR2 specific data SCANNAME=racnode12-scan SCANIP=192.168.1.50

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• SCHA API for resource group failover / switchover history

  - by krishna.k.murthy

  The Oracle Solaris Cluster framework keeps an internal log of cluster events, including switchover and failover of resource groups. These logs can be useful to Oracle support engineers for diagnosing cluster behavior. However, till now, there was no external interface to access the event history. Oracle Solaris Cluster 4.2 provides a new API option for viewing the recent history of resource group switchovers in a program-parsable format. Oracle Solaris Cluster 4.2 provides a new option tag argument RG_FAILOVER_LOG for the existing API command scha_cluster_get which can be used to list recent failover / switchover events for resource groups. The command usage is as shown below: # scha_cluster_get -O RG_FAILOVER_LOG number_of_days number_of_days : the number of days to be considered for scanning the historical logs. The command returns a list of events in the following format. Each field is separated by a semi-colon [;]: resource_group_name;source_nodes;target_nodes;time_stamp source_nodes: node_names from which resource group is failed over or was switched manually. target_nodes: node_names to which the resource group failed over or was switched manually. There is a corresponding enhancement in the C API function scha_cluster_get() which uses the SCHA_RG_FAILOVER_LOG query tag. In the example below geo-infrastructure (failover resource group), geo-clusterstate (scalable resource group), oracle-rg (failover resource group), asm-dg-rg (scalable resource group) and asm-inst-rg (scalable resource group) are part of Geographic Edition setup. # /usr/cluster/bin/scha_cluster_get -O RG_FAILOVER_LOG 3 geo-infrastructure;schost1c;;Mon Jul 21 15:51:51 2014 geo-clusterstate;schost2c,schost1c;schost2c;Mon Jul 21 15:52:26 2014 oracle-rg;schost1c;;Mon Jul 21 15:54:31 2014 asm-dg-rg;schost2c,schost1c;schost2c;Mon Jul 21 15:54:58 2014 asm-inst-rg;schost2c,schost1c;schost2c;Mon Jul 21 15:56:11 2014 oracle-rg;;schost2c;Mon Jul 21 15:58:51 2014 geo-infrastructure;;schost2c;Mon Jul 21 15:59:19 2014 geo-clusterstate;schost2c;schost2c,schost1c;Mon Jul 21 16:01:51 2014 asm-inst-rg;schost2c;schost2c,schost1c;Mon Jul 21 16:01:10 2014 asm-dg-rg;schost2c;schost2c,schost1c;Mon Jul 21 16:02:10 2014 oracle-rg;schost2c;;Tue Jul 22 16:58:02 2014 oracle-rg;;schost1c;Tue Jul 22 16:59:05 2014 oracle-rg;schost1c;schost1c;Tue Jul 22 17:05:33 2014 Note that in the output some of the entries might have an empty string in the source_nodes. Such entries correspond to events in which the resource group is switched online manually or during a cluster boot-up. Similarly, an empty destination_nodes list indicates an event in which the resource group went offline. - Arpit Gupta, Harish Mallya

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• Good, simple reasons for having a multiple environments

  - by smp7d

  Throughout my career I had worked at companies that had a collection of different environments for different purposes. We always had more or less our desktop environment, a test environment, a QA environment, a staging environment and a production environment. This went for both servers/applications and any data sources we were using. When I started at my current company I found that 90% of the apps were either developed on a desktop environment against production data sources or developed directly on the production server depending on the platform. I wasn't phased because I was hired in part to make changes to improve the way the development team functioned, which was clear from my interview process. We slowly started to turn the philosophy and pretty soon, most of the apps could be run in either a desktop, test or production environment. Not too long after that staging came around as well. Now most of our developers see the benefit of this methodology and defend it vigilantly. However, we have a number of legacy apps that never got migrated. We also have a number of legacy programmers who think of this as a waste of time. Unfortunately, we got lip service but never full buy-in from management. We got what we thought was a commitment to invest substantially in this about a year ago, but nothing materialized despite the considerable planning that we put into it. Now we are finding that we need more and more environments. We need help from the server/network administration teams for setup and we need participation from the business stakeholders to support the release cycle. We are at a place now where a project can function what I consider "normally" only if you have the right people on the project and the time to set up the proper environments. I'd love to present a complete argument, but management really has no time and interest in hearing me out until there is a critical issue. I cant really articulate the benefits simply as it always just seemed second nature to me. I was wondering if there are any good, simple, irrefutable reasons for the separation of environments that would get managers with no development experience to get behind this idea. Are there any good resources/literature on the topic?

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• Obtaining positional information in the IEnumerable Select extension method

  - by Kyle Burns

  This blog entry is intended to provide a narrow and brief look into a way to use the Select extension method that I had until recently overlooked. Every developer who is using IEnumerable extension methods to work with data has been exposed to the Select extension method, because it is a pretty critical piece of almost every query over a collection of objects.  The method is defined on type IEnumerable and takes as its argument a function that accepts an item from the collection and returns an object which will be an item within the returned collection.  This allows you to perform transformations on the source collection.  A somewhat contrived example would be the following code that transforms a collection of strings into a collection of anonymous objects: 1: var media = new[] {"book", "cd", "tape"}; 2: var transformed = media.Select( item => 3: { 4: Media = item 5: } ); This code transforms the array of strings into a collection of objects which each have a string property called Media. If every developer using the LINQ extension methods already knows this, why am I blogging about it?  I’m blogging about it because the method has another overload that I hadn’t seen before I needed it a few weeks back and I thought I would share a little about it with whoever happens upon my blog.  In the other overload, the function defined in the first overload as: 1: Func<TSource, TResult> is instead defined as: 1: Func<TSource, int, TResult>   The additional parameter is an integer representing the current element’s position in the enumerable sequence.  I used this information in what I thought was a pretty cool way to compare collections and I’ll probably blog about that sometime in the near future, but for now we’ll continue with the contrived example I’ve already started to keep things simple and show how this works.  The following code sample shows how the positional information could be used in an alternating color scenario.  I’m using a foreach loop because IEnumerable doesn’t have a ForEach extension, but many libraries do add the ForEach extension to IEnumerable so you can update the code if you’re using one of these libraries or have created your own. 1: var media = new[] {"book", "cd", "tape"}; 2: foreach (var result in media.Select( 3: (item, index) => 4: new { Item = item, Index = index })) 5: { 6: Console.ForegroundColor = result.Index % 2 == 0 7: ? ConsoleColor.Blue : ConsoleColor.Yellow; 8: Console.WriteLine(result.Item); 9: }

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• Should Exterrnal USB hard drive auto mount Ubuntu 12.04.01 LTS

  - by Chris Good

  I want to have external USB hard drives automatically mounted when plugged in. I have 2 drives exactly the same except for volume label. They both have the same UUID. I want to be easily able to swap them as I'm using them for backups and want to keep 1 at home for off site backup. I've set up the /etc/fstab so they should mount at different places based on their volume label: /etc/fstab : LABEL=Passport1 /media/Passport1 ntfs defaults,windows_names,locale=en_US.utf8 0 0 LABEL=Passport2 /media/Passport2 ntfs defaults,windows_names,locale=en_US.utf8 0 0 blkid shows : ... /dev/sdc1: LABEL="Passport2" UUID="4E1AEA7B1AEA6007" TYPE="ntfs" /dev/sdd1: LABEL="Passport1" UUID="4E1AEA7B1AEA6007" TYPE="ntfs" They both mount automatically during reboot but do not mount when just plugged in to a running system. I've read lots of stuff about this, much of it is old so I'm not sure if it applies. I've read some stuff that says the mounts should happen automatically when plugged in, and lots of other stuff that says you have to install other software to make this happen, although much of it just seems to set up the fstab. What's the real story? Here is /var/log/syslog when drive is plugged in: Dec 14 11:22:58 ausyvutims1 kernel: [66221.300196] usb 1-1: new high-speed USB device number 6 using ehci_hcd Dec 14 11:22:58 ausyvutims1 mtp-probe: checking bus 1, device 6: "/sys/devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1" Dec 14 11:22:58 ausyvutims1 mtp-probe: bus: 1, device: 6 was not an MTP device Dec 14 11:22:58 ausyvutims1 kernel: [66221.656020] scsi7 : usb-storage 1-1:1.0 Dec 14 11:22:59 ausyvutims1 kernel: [66222.661534] scsi 7:0:0:0: Direct-Access WD My Passport 0748 1016 PQ: 0 ANSI: 6 Dec 14 11:22:59 ausyvutims1 kernel: [66222.666466] scsi 7:0:0:1: Enclosure WD SES Device 1016 PQ: 0 ANSI: 6 Dec 14 11:22:59 ausyvutims1 kernel: [66222.667739] sd 7:0:0:0: Attached scsi generic sg3 type 0 Dec 14 11:22:59 ausyvutims1 kernel: [66222.667913] ses 7:0:0:1: Attached Enclosure device Dec 14 11:22:59 ausyvutims1 kernel: [66222.668047] ses 7:0:0:1: Attached scsi generic sg4 type 13 Dec 14 11:22:59 ausyvutims1 kernel: [66222.678473] sd 7:0:0:0: [sdc] 1953458176 512-byte logical blocks: (1.00 TB/931 GiB) Dec 14 11:22:59 ausyvutims1 kernel: [66222.687700] sd 7:0:0:0: [sdc] Write Protect is off Dec 14 11:22:59 ausyvutims1 kernel: [66222.687705] sd 7:0:0:0: [sdc] Mode Sense: 47 00 10 08 Dec 14 11:22:59 ausyvutims1 kernel: [66222.701076] sd 7:0:0:0: [sdc] No Caching mode page present Dec 14 11:22:59 ausyvutims1 kernel: [66222.701081] sd 7:0:0:0: [sdc] Assuming drive cache: write through Dec 14 11:22:59 ausyvutims1 kernel: [66222.738062] sd 7:0:0:0: [sdc] No Caching mode page present Dec 14 11:22:59 ausyvutims1 kernel: [66222.738068] sd 7:0:0:0: [sdc] Assuming drive cache: write through Dec 14 11:22:59 ausyvutims1 kernel: [66222.754558] sdc: sdc1 Dec 14 11:22:59 ausyvutims1 kernel: [66222.792006] sd 7:0:0:0: [sdc] No Caching mode page present Dec 14 11:22:59 ausyvutims1 kernel: [66222.792012] sd 7:0:0:0: [sdc] Assuming drive cache: write through Dec 14 11:22:59 ausyvutims1 kernel: [66222.792016] sd 7:0:0:0: [sdc] Attached SCSI disk Dec 14 11:22:59 ausyvutims1 ata_id[16971]: HDIO_GET_IDENTITY failed for '/dev/sdc': Invalid argument Thanks for any help offered

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• How to suggest using an ORM instead of stored procedures?

  - by Wayne M

  I work at a company that only uses stored procedures for all data access, which makes it very annoying to keep our local databases in sync as every commit we have to run new procs. I have used some basic ORMs in the past and I find the experience much better and cleaner. I'd like to suggest to the development manager and rest of the team that we look into using an ORM Of some kind for future development (the rest of the team are only familiar with stored procedures and have never used anything else). The current architecture is .NET 3.5 written like .NET 1.1, with "god classes" that use a strange implementation of ActiveRecord and return untyped DataSets which are looped over in code-behind files - the classes work something like this: class Foo { public bool LoadFoo() { bool blnResult = false; if (this.FooID == 0) { throw new Exception("FooID must be set before calling this method."); } DataSet ds = // ... call to Sproc if (ds.Tables[0].Rows.Count > 0) { foo.FooName = ds.Tables[0].Rows[0]["FooName"].ToString(); // other properties set blnResult = true; } return blnResult; } } // Consumer Foo foo = new Foo(); foo.FooID = 1234; foo.LoadFoo(); // do stuff with foo... There is pretty much no application of any design patterns. There are no tests whatsoever (nobody else knows how to write unit tests, and testing is done through manually loading up the website and poking around). Looking through our database we have: 199 tables, 13 views, a whopping 926 stored procedures and 93 functions. About 30 or so tables are used for batch jobs or external things, the remainder are used in our core application. Is it even worth pursuing a different approach in this scenario? I'm talking about moving forward only since we aren't allowed to refactor the existing code since "it works" so we cannot change the existing classes to use an ORM, but I don't know how often we add brand new modules instead of adding to/fixing current modules so I'm not sure if an ORM is the right approach (too much invested in stored procedures and DataSets). If it is the right choice, how should I present the case for using one? Off the top of my head the only benefits I can think of is having cleaner code (although it might not be, since the current architecture isn't built with ORMs in mind so we would basically be jury-rigging ORMs on to future modules but the old ones would still be using the DataSets) and less hassle to have to remember what procedure scripts have been run and which need to be run, etc. but that's it, and I don't know how compelling an argument that would be. Maintainability is another concern but one that nobody except me seems to be concerned about.

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• Real-Time Multi-User Gaming Platform

  - by Victor Engel

  I asked this question at Stack Overflow but was told it's more appropriate here, so I'm posting it again here. I'm considering developing a real-time multi-user game, and I want to gather some information about possibilities before I do some real development. I've thought about how best to ask the question, and for simplicity, the best way that occurred to me was to make an analogy to the field (or playground) game darebase. In the field game of darebase, there are two or more bases. To start, there is one team on each base. The game is a fancy game of tag. When two people meet out in the field, the person who left his base most recently timewise captures the other person. They then return to that person's base. Play continues until everyone is part of the same team. So, analogizing this to an online computer game, let's suppose there are an indefinite number of bases. When a person starts up the game, he has a team that is located at, for example, his current GPS coordinates. It could be a virtual world, but for sake of argument, let's suppose the virtual world corresponds to the player's actual GPS coordinates. The game software then consults the database to see where the closest other base is that is online, and the two teams play their game of virtual tag. Note that the user of the other base could have a different base than the one run by the current user as the closest base to him, in which case, he would be in two simultaneous battles, one with each base. When they go offline, the state of their players is saved on a server somewhere. Game logic calls for the players to have some automaton-logic of some sort, so they can fend for themselves in a limited way using basic rules, until their user goes online again. The user doesn't control the players' movements directly, but issues general directives that influence the players' movement logic. I think this analogy is good enough to frame my question. What sort of platforms are available to develop this sort of game? I've been looking at smartfoxserver, but I'm not convinced yet that it is the best option or even that it will work at all. One possibility, of course, would be to roll out my own web server, but I'd rather not do that if there is an existing service out there already that I could tap into. I will be developing for iOS devices at first. So any suggestions would be greatly appreciated. I think I need to establish the architecture first before proceeding with this project. Note that darbase is not the game I intend to implement, but, upon reflection, that might not be a bad idea either.

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• Is code like this a "train wreck" (in violation of Law of Demeter)?

  - by Michael Kjörling

  Browsing through some code I've written, I came across the following construct which got me thinking. At a first glance, it seems clean enough. Yes, in the actual code the getLocation() method has a slightly more specific name which better describes exactly which location it gets. service.setLocation(this.configuration.getLocation().toString()); In this case, service is an instance variable of a known type, declared within the method. this.configuration comes from being passed in to the class constructor, and is an instance of a class implementing a specific interface (which mandates a public getLocation() method). Hence, the return type of the expression this.configuration.getLocation() is known; specifically in this case, it is a java.net.URL, whereas service.setLocation() wants a String. Since the two types String and URL are not directly compatible, some sort of conversion is required to fit the square peg in the round hole. However, according to the Law of Demeter as cited in Clean Code, a method f in class C should only call methods on C, objects created by or passed as arguments to f, and objects held in instance variables of C. Anything beyond that (the final toString() in my particular case above, unless you consider a temporary object created as a result of the method invocation itself, in which case the whole Law seems to be moot) is disallowed. Is there a valid reasoning why a call like the above, given the constraints listed, should be discouraged or even disallowed? Or am I just being overly nitpicky? If I were to implement a method URLToString() which simply calls toString() on a URL object (such as that returned by getLocation()) passed to it as a parameter, and returns the result, I could wrap the getLocation() call in it to achieve exactly the same result; effectively, I would just move the conversion one step outward. Would that somehow make it acceptable? (It seems to me, intuitively, that it should not make any difference either way, since all that does is move things around a little. However, going by the letter of the Law of Demeter as cited, it would be acceptable, since I would then be operating directly on a parameter to a function.) Would it make any difference if this was about something slightly more exotic than calling toString() on a standard type? When answering, do keep in mind that altering the behavior or API of the type that the service variable is of is not practical. Also, for the sake of argument, let's say that altering the return type of getLocation() is also impractical.

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• Why would I learn C++11, having known C and C++?

  - by Shahbaz

  I am a programmer in C and C++, although I don't stick to either language and write a mixture of the two. Sometimes having code in classes, possibly with operator overloading, or templates and the oh so great STL is obviously a better way. Sometimes use of a simple C function pointer is much much more readable and clear. So I find beauty and practicality in both languages. I don't want to get into the discussion of "If you mix them and compile with a C++ compiler, it's not a mix anymore, it's all C++" I think we all understand what I mean by mixing them. Also, I don't want to talk about C vs C++, this question is all about C++11. C++11 introduces what I think are significant changes to how C++ works, but it has introduced many special cases that change how different features behave in different circumstances, placing restrictions on multiple inheritance, adding lambda functions, etc. I know that at some point in the future, when you say C++ everyone would assume C++11. Much like when you say C nowadays, you most probably mean C99. That makes me consider learning C++11. After all, if I want to continue writing code in C++, I may at some point need to start using those features simply because my colleagues have. Take C for example. After so many years, there are still many people learning and writing code in C. Why? Because the language is good. What good means is that, it follows many of the rules to create a good programming language. So besides being powerful (which easy or hard, almost all programming languages are), C is regular and has few exceptions, if any. C++11 however, I don't think so. I'm not sure that the changes introduced in C++11 are making the language better. So the question is: Why would I learn C++11? Update: My original question in short was: "I like C++, but the new C++11 doesn't look good because of this and this and this. However, deep down something tells me I need to learn it. So, I asked this question here so that someone would help convince me to learn it." However, the zealous people here can't tolerate pointing out a flaw in their language and were not at all constructive in this manner. After the moderator edited the question, it became more like a "So, how about this new C++11?" which was not at all my question. Therefore, in a day or too I am going to delete this question if no one comes up with an actual convincing argument. P.S. If you are interested in knowing what flaws I was talking about, you can edit my question and see the previous edits.

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• C# 5: At last, async without the pain

  - by Alex.Davies

  For me, the best feature in Visual Studio 11 is the async and await keywords that come with C# 5. I am a big fan of asynchronous programming: it frees up resources, in particular the thread that a piece of code needs to run in. That lets that thread run something else, while waiting for your long-running operation to complete. That's really important if that thread is the UI thread, or if it's holding a lock because it accesses some data structure. Before C# 5, I think I was about the only person in the world who really cared about asynchronous programming. The trouble was that you had to go to extreme lengths to make code asynchronous. I would forever be writing methods that, instead of returning a value, accepted an extra argument that is a "continuation". Then, when calling the method, I'd have to pass a lambda in to it, which contained all the stuff that needed to happen after the method finished. Here is a real snippet of code that is in .NET Demon: m_BuildControl.FilterEnabledForBuilding(     projects,     enabledProjects = m_OutOfDateProjectFinder.FilterNeedsBuilding(         enabledProjects,         newDirtyProjects =         {             // Mark any currently broken projects as dirty             newDirtyProjects.UnionWith(m_BrokenProjects);             // Copy what we found into the set of dirty things             m_DirtyProjects = newDirtyProjects;             RunSomeBuilds();         })); It's just obtuse. Who puts a lambda inside a lambda like that? Well, me obviously. But surely enabledProjects should just be the return value of FilterEnabledForBuilding? And newDirtyProjects should just be the return value of FilterNeedsBuilding? C# 5 async/await lets you write asynchronous code without it looking so stupid. Here's what I plan to change that code to, once we upgrade to VS 11: var enabledProjects = await m_BuildControl.FilterEnabledForBuilding(projects); var newDirtyProjects = await m_OutOfDateProjectFinder.FilterNeedsBuilding(enabledProjects); // Mark any currently broken projects as dirty newDirtyProjects.UnionWith(m_BrokenProjects); // Copy what we found into the set of dirty things m_DirtyProjects = newDirtyProjects; RunSomeBuilds(); Much easier to read! But how is this the same code? If we were on the UI thread, doesn't the UI thread have to block while FilterEnabledForBuilding runs? No, it doesn't, and that's the magic of the await keyword! It cuts your method up into its constituent pieces, much like I did manually with lambdas before. When you run it, only the piece up to the first await actually runs. The rest is passed to FilterEnabledForBuilding as a continuation, which will get called back whenever that method is finished. In the meantime, our thread returns, and can go back to making the UI responsive, or whatever else threads do in their spare time. This is actually a massive simplification, and if you're interested in all the gory details, and speed hacks that the await keyword actually does for you, I recommend Jon Skeet's blog posts about it.

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• How can I achieve a 3D-like effect with spritebatch's rotation and scale parameters

  - by Alic44

  I'm working on a 2d game with a top-down perspective similar to Secret of Mana and the 2D Final Fantasy games, with one big difference being that it's an action rpg using a 3-dimensional physics engine. I'm trying to draw an aimer graphic (basically an arrow) at my characters' feet when they're aiming a ranged weapon. At first I just converted the character's aim vector to radians and passed that into spritebatch, but there was a problem. The position of every object in my world is scaled for perspective when it's drawn to the screen. So if the physics engine coordinates are (1, 0, 1), the screen coords are actually (1, .707) -- the Y and Z axis are scaled by a perspective factor of .707 and then added together to get the screen coordinates. This meant that the direction the aimer graphic pointed (thanks to its rotation value passed into spritebatch) didn't match up with the direction the projectile actually traveled over time. Things looked fine when the characters fired left, right, up, or down, but if you fired on a diagonal the perspective of the physics engine didn't match with the simplistic way I was converting the character's aim direction to a screen rotation. Ok, fast forward to now: I've got the aimer's rotation matched up with the path the projectile will actually take, which I'm doing by decomposing a transform matrix which I build from two rotation matrices (one to represent the aimer's rotation, and one to represent the camera's 45 degree rotation on the x axis). My question is, is there a way to get not just rotation from a series of matrix transformations, but to also get a Vector2 scale which would give the aimer the appearance of being a 3d object, being warped by perspective? Orthographic perspective is what I'm going for, I think. So, the aimer arrow would get longer when facing sideways, and shorter when facing north and south because of the perspective. At the same time, it would get wider when facing north and south, and less wide when facing right or left. I'd like to avoid actually drawing the aimer texture in 3d because I'm still using spritebatch's layerdepth parameter at this point in my project, and I don't want to have to figure out how to draw a 3d object within the depth sorting system I already have. I can provide code and more details if this is too vague as a question... This is my first post on stack exchange. Thanks a lot for reading! Note: (I think) I realize it can't be a technically correct 3D perspective, because the spritebatch's vector2 scaling argument doesn't allow for an object to be skewed the way it actually should be. What I'm really interested in is, is there a good way to fake the effect, or should I just drop it and not scale at all? Edit to clarify without the help of a picture (apparently I can't post them yet): I want the aimer arrow to look like it has been painted on the ground at the character's feet, so it should appear to be drawn on the ground plane (in my case the XZ plane) which should be tilted at a 45 degree angle (around the X axis) from the viewing perspective. Alex

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• Live-Ubuntu 12.04 ran fine, now stopped booting!

  - by user89743

  I've seen similar problems to this several times in the forum, but mine is a bit different, so the other posts I saw were no help to me. When I boot Ubuntu 12.04 64-bit from live-SD-card (3GB persistence) I suddenly get this error: (initramfs) mount: mounting /dev/loop0 on //filesystem.squashfs failed: Invalid argument Can not mount /dev/loop/0 (/cdrom/casper/filesystem.squashfs) on //filesystem.squashfs (it says I can type "help" for commands, but I don't know anything about how to go from there, totally new to linux) The reason I say my case is different is because my Ubuntu worked fine for over a week, even pretty fast, and now this problem happened. Before that I used to run my live ubuntu from USB sticks but that was slower (especially when booting which took 15 minutes from USB stick!). Also I kept getting the same above problem after a while when booting and had to re-create a live USB linux several times. Installing on harddrive is not an option because my harddrive has physical damage and getting a replacement will take a while, therefore I can only use live-USB or live-SD-card Ubuntu. As I said I used Ubuntu without problems for more than a week, before that as well for several weeks on USB sticks, but the above problem occured sooner or later. This time I paid attention to when it happened: I was rebooting my computer (HP 620 laptop, 4 GB RAM, 64 bit system) from SD flash card and when I was booting I selected F6 and then the first option "no acpi" or something like that...I had used it before and noticed it slowed down the time it took Linux to use. This time it caused this error. Now even when I boot normally/default I get this error. Now I'm accessing Ubuntu from my USB stick without persistence file, when I check my SD card, all the files mentioned in the error message are there and the filesystem.squashfs is 691.2 MB so nothing seems to have been deleted by accident. (I have already made many changes/downloaded programs to my SD card persistent Ubuntu and would hope to loose them, since downloading is expensive for me, and since the problem seems to re-occur...) Can anyone help me, preferably without having to create another startup disk on my SD card? I'm totally new to this. Sorry for the long posts, just didn't know what info is relevant and what isnt! Kon

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• Good, simple reasons for having multiple environments

  - by smp7d

  Throughout my career I had worked at companies that had a collection of different environments for different purposes. We always had more or less our desktop environment, a test environment, a QA environment, a staging environment and a production environment. This went for both servers/applications and any data sources we were using. When I started at my current company I found that 90% of the apps were either developed on a desktop environment against production data sources or developed directly on the production server depending on the platform. I wasn't fazed because I was hired in part to make changes to improve the way the development team functioned, which was clear from my interview process. We slowly started to turn the philosophy and pretty soon, most of the apps could be run in either a desktop, test or production environment. Not too long after that staging came around as well. Now most of our developers see the benefit of this methodology and defend it vigilantly. However, we have a number of legacy apps that never got migrated. We also have a number of legacy programmers who think of this as a waste of time. Unfortunately, we got lip service but never full buy-in from management. We got what we thought was a commitment to invest substantially in this about a year ago, but nothing materialized despite the considerable planning that we put into it. Now we are finding that we need more and more environments. We need help from the server/network administration teams for setup and we need participation from the business stakeholders to support the release cycle. We are at a place now where a project can function what I consider "normally" only if you have the right people on the project and the time to set up the proper environments. I'd love to present a complete argument, but management really has no time and interest in hearing me out until there is a critical issue. I can't really articulate the benefits simply as it always just seemed second nature to me. I was wondering if there are any good, simple, irrefutable reasons for the separation of environments that would get managers with no development experience to get behind this idea. Are there any good resources/literature on the topic?

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• To make or not to make...python-nautilus a dependency?

  - by George Edison

  That is the question! Okay, all silliness aside, I really am forced to make a difficult decision here. My application is written in C++ and allows other scripts to invoke methods via XML-RPC. One of these scripts is a Nautilus extension written in Python. The extension is packaged with the rest of the application and copied to the appropriate place when installed (/usr/share/nautilus-python/extensions). Now the problem is that the Nautilus extension requires the python-nautilus package to be installed to be operational. So therefore I have three options: Make the python-nautilus package a dependency. This option will ensure that anyone who installs my package will be able to use the Nautilus extension. However, this option will not be attractive to XFCE or KDE users - a ton of python-nautilus's dependencies will be installed on their machines and take up a lot of space - even if they never use Nautilus. Put the python-nautilus package in the suggests: or recommends: field. This option provides the end-user with a way to avoid installing the python-nautilus package (by providing the --no-install-suggests or --no-install-recommends argument to apt-get). However, this won't work when the user installs the package in the Software Center. (I always get mixed up as to which of those two fields are installed by default.) Prompt the user when the application is installed or first launched. This option is more complicated than the others but offers the best compromise between making it easy for the user to install python-nautilus (without going into a technical explanation) and not installing it when the user doesn't need it (or want it). I guess the best way to implement this is a simple prompt that invokes apt-get if the user would like the package installed. Don't install the package at all. This option ensures that nobody has python-nautilus installed on their machine unless they want it. However, this also means that my Nautilus extension will simply not run on the end-user's machine unless they manually install the package. Which of these options seems the best choice? Have I missed any pros and cons for each of the options?

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• Reasons to Use a VM For Development

  - by George Stocker

  Background: I work at a start-up company, where one team uses Virtual Machines to connect to a remote server to do their development, and another team (the team I'm on) uses local IIS/SQL Server 2005/Visual Studio installations to conduct work. Team VM is located about 1000 miles from Team Non-VM, and the servers the VMs run off of are located near Team VM (Latency, for those that are wondering, is about 50ms). A person high in the company is pushing for Team Non-VM to use virtual machines for programming, development, and testing. The latter point we agree on -- we want Virtual Machines to test configurations and various aspects of the web application in a 'clean' state. The Problem: What we don't agree on is having developers using RDP to connect to a desktop remotely that contains Visual Studio, SQL Server, and IIS to do the same development we could do locally on our laptops. I've tried the VM set-up, and besides the color issue, there is a latency issue that is rather noticeable, not to mention that since we're a start-up, a good number of employees work from home on occasion with our work laptops, and this move would cut off the laptops. They'd be turned in. Reasons to Use Remote VMs for Development (Not Testing!): Here are the stated reasons that this person wants us to use VMs: They work for TeamVM. They keep the source code "safe". If we want to work from home, we could just use our home PCs. Licenses (I don't know what the argument is, only that it's been used). Reasons not to use Remote VMs for Development: Here are the stated reasons why we don't want to use VMs: We like working from home. We get a lot done on our own time. We're not going to use our Home PCs to do work related stuff. The Latency is noticeable. Support for the VMs (if they go down, or if we need a new VM) takes a while. We don't have administrative privileges on the VM, and are unable to change settings as needed. What I'm looking for from the community is this: What reasons would you give for not using VMs for development? Keep in mind these are remote VMs -- this isn't a VM running on a local desktop. It's using the laptop (or a desktop) as a thin client for a remote VM. Also, on the other side of the coin: Is there something we're missing that makes VMs more palatable for development? Edit: I think 'safe' is used in term of corporate espionage, or more correctly if the Laptop gets stolen, the person who stole would have access to our source code. The former (as we've pointed out, is always going to be a possibility -- companies stop that with litigation, there isn't a technical solution (so far as I can see)). The latter point is ( though I don't know its usefulness in a corporate scenario) mitigated by Truecrypt'ing the entire volume.

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• How to specialize a c++ variadic template?

  - by Serge

  I'm trying to understand c++ variadic templates. I'm not much aware of the correct language to use to explain what I'd like to achieve, so it might be simpler if I provide a bit of code which illustrate what I'd like to achieve. #include <iostream> #include <string> using namespace std; template<int ...A> class TestTemplate1 { public: string getString() { return "Normal"; } }; template<int T, int ...A> string TestTemplate1<2, A...>::getString() { return "Specialized"; } template<typename ...A> class TestTemplate2 { }; int main() { TestTemplate1<1, 2, 3, 4> t1_1; TestTemplate1<1, 2> t1_2; TestTemplate1<> t1_3; TestTemplate1<2> t1_4; TestTemplate2<> t2_1; TestTemplate2<int, double> t2_2; cout << t1_1.getString() << endl; cout << t1_2.getString() << endl; cout << t1_3.getString() << endl; cout << t1_4.getString() << endl; } This throws several errors. error C2333: 'TestTemplate1<::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2,3,4::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<2::getString' : error in function declaration; skipping function body error C2977: 'TestTemplate1' : too many template arguments error C2995: 'std::string TestTemplate1::getString(void)' : function template has already been defined error C3860: template argument list following class template name must list parameters in the order used in template parameter list How can I have a specialized behavior for every TestTemplate1<2, ...> instances like t1_4?

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• Are closures with side-effects considered "functional style"?

  - by Giorgio

  Many modern programming languages support some concept of closure, i.e. of a piece of code (a block or a function) that Can be treated as a value, and therefore stored in a variable, passed around to different parts of the code, be defined in one part of a program and invoked in a totally different part of the same program. Can capture variables from the context in which it is defined, and access them when it is later invoked (possibly in a totally different context). Here is an example of a closure written in Scala: def filterList(xs: List[Int], lowerBound: Int): List[Int] = xs.filter(x => x >= lowerBound) The function literal x => x >= lowerBound contains the free variable lowerBound, which is closed (bound) by the argument of the function filterList that has the same name. The closure is passed to the library method filter, which can invoke it repeatedly as a normal function. I have been reading a lot of questions and answers on this site and, as far as I understand, the term closure is often automatically associated with functional programming and functional programming style. The definition of function programming on wikipedia reads: In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state. and further on [...] in functional code, the output value of a function depends only on the arguments that are input to the function [...]. Eliminating side effects can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming. On the other hand, many closure constructs provided by programming languages allow a closure to capture non-local variables and change them when the closure is invoked, thus producing a side effect on the environment in which they were defined. In this case, closures implement the first idea of functional programming (functions are first-class entities that can be moved around like other values) but neglect the second idea (avoiding side-effects). Is this use of closures with side effects considered functional style or are closures considered a more general construct that can be used both for a functional and a non-functional programming style? Is there any literature on this topic? IMPORTANT NOTE I am not questioning the usefulness of side-effects or of having closures with side effects. Also, I am not interested in a discussion about the advantages / disadvantages of closures with or without side effects. I am only interested to know if using such closures is still considered functional style by the proponent of functional programming or if, on the contrary, their use is discouraged when using a functional style.

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• More elegant way to avoid hard coding the format of a a CSV file?

  - by dsollen

  I know this is trivial issue, but I just feel this can be more elegant. So I need to write/read data files for my program, lets say they are CSV for now. I can implement the format as I see fit, but I may have need to change that format later. The simply thing to do is something like out.write(For.getValue()+","+bar.getMinValue()+","+fi.toString()); This is easy to write, but obviously is guilty of hard coding and the general 'magic number' issue. The format is hard-coded, requires parsing of the code to figure out the file format, and changing the format requires changing multiple methods. I could instead have my constants specifying the location that I want each variable to be saved in the CSV file to remove some of the 'magic numbers'; then save/load into the an array at the location specified by the constants: int FOO_LOCATION=0; int BAR_MIN_VAL_LOCATION=1; int FI_LOCATION=2 int NUM_ARGUMENTS=3; String[] outputArguments=new String[NUM_ARGUMENTS]; outputArguments[FOO_LOCATION] = foo.getValue(); outputArgumetns[BAR_MIN_VAL_LOCATION] = bar.getMinValue(); outptArguments[FI_LOCATOIN==fi.toString(); writeAsCSV(outputArguments); But this is...extremely verbose and still a bit ugly. It makes it easy to see the format of existing CSV and to swap the location of variables within the file easily. However, if I decide to add an extra value to the csv I need to not only add a new constant, but also modify the read and write methods to add the logic that actually saves/reads the argument from the array; I still have to hunt down every method using these variables and change them by hand! If I use Java enums I can clean this up slightly, but the real issue is still present. Short of some sort of functional programming (and java's inner classes are too ugly to be considered functional) I still have no obvious way of clearly expressing what variable is associated with each constant short of writing (and maintaining) it in the read/write methods. For instance I still need to write somewhere that the FOO_LOCATION specifies the location of foo.getValue(). It seems as if there should be a prettier, easier to maintain, manner for approaching this? Incidentally, I'm working in java at the moment, however, I am interested conceptually about the design approach regardless of language. Some library in java that does all the work for me is definitely welcome (though it may prove more hassle to get permission to add it to the codebase then to just write something by hand quickly), but what I'm really asking is more about how to write elegant code if you had to do this by hand.

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• Code Design question, circular reference across classes?

  - by dsollen

  I have no code here, as this is more of a design question (I assume this is still the best place to ask it). I have a very simple server in java which stores a mapping between certain values and UUID which are to be used by many systems across multiple platforms. It accepts a connection from a client and creates a clientSocket which stores the socket and all the other relevant data unique to that connection. Each clientSocket will run in their own thread and will block on the socket waiting for a read. I expect very little strain on this system, it will rarely get called, but when it does get a call it will need to respond quickly and due to the risk of it having a peak time with multiple calls coming in at once threaded is still better. Each thread has a reference to a Mapper class which stores the mapping of UUID which it's reporting to others (with proper synchronization of course). This all works until I have to add a new UUID to the list. When this happens I want to report to all clients that care about that particular UUID that a new one was added. I can't multicast (limitation of the system I'm running on) so I'm having each socket send the message to the client through the established socket. However, since each thread only knows about the socket it's waiting on I didn't have a clear method of looking up every thread/socket that cares about the data to inform them of the new UUID. Polling is out mostly because it seems a little too convoluted to try to maintain a list of newly added UUID. My solution as of now is to have the 'parent' class which creates the mapper class and spawns all the threads pass itself as an argument to the mapper. Then when the mapper creates a new UUID it can make a call to the parent class telling it to send out updates to all the other sockets that care about the change. I'm concerned that this may be a bad design due to the use of a circular reference; parent has a reference to mapper (to pass it to new ClientSocket threads) and mapper points to parent. It doesn't really feel like a bad design to me but I wanted to check since circular references are suppose to be bad. Note: I realize this means that the thread associated with whatever socket originally received the request that spawned the creation of a UUID is going to pay the 'cost' of outputting to all the other clients that care about the new UUID. I don't care about this; as I said I suspect the client to receive only intermittent messages. It's unlikely for one socket to receive multiple messages at one time, and there won't be that many sockets so it shouldn't take too long to send messages to each of them. Perhaps later I'll fix the fact that I'm saddling higher work load on whatever unfortunate thread gets the first request; but for now I think it's fine.

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• Validation and Error Generation when using the Data Mapper Pattern

  - by AndyPerlitch

  I am working on saving state of an object to a database using the data mapper pattern, but I am looking for suggestions/guidance on the validation and error message generation step (step 4 below). Here are the general steps as I see them for doing this: (1) The data mapper is used to get current info (assoc array) about the object in db: +=====================================================+ | person_id | name | favorite_color | age | +=====================================================+ | 1 | Andy | Green | 24 | +-----------------------------------------------------+ mapper returns associative array, eg. Person_Mapper::getPersonById($id) : $person_row = array( 'person_id' => 1, 'name' => 'Andy', 'favorite_color' => 'Green', 'age' => '24', ); (2) the Person object constructor takes this array as an argument, populating its fields. class Person { protected $person_id; protected $name; protected $favorite_color; protected $age; function __construct(array $person_row) { $this->person_id = $person_row['person_id']; $this->name = $person_row['name']; $this->favorite_color = $person_row['favorite_color']; $this->age = $person_row['age']; } // getters and setters... public function toArray() { return array( 'person_id' => $this->person_id, 'name' => $this->name, 'favorite_color' => $this->favorite_color, 'age' => $this->age, ); } } (3a) (GET request) Inputs of an HTML form that is used to change info about the person is populated using Person::getters <form> <input type="text" name="name" value="<?=$person->getName()?>" /> <input type="text" name="favorite_color" value="<?=$person->getFavColor()?>" /> <input type="text" name="age" value="<?=$person->getAge()?>" /> </form> (3b) (POST request) Person object is altered with the POST data using Person::setters $person->setName($_POST['name']); $person->setFavColor($_POST['favorite_color']); $person->setAge($_POST['age']); *(4) Validation and error message generation on a per-field basis - Should this take place in the person object or the person mapper object? - Should data be validated BEFORE being placed into fields of the person object? (5) Data mapper saves the person object (updates row in the database): $person_mapper->savePerson($person); // the savePerson method uses $person->toArray() // to get data in a more digestible format for the // db gateway used by person_mapper Any guidance, suggestions, criticism, or name-calling would be greatly appreciated.

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• Office lights on or off in programming department? How to decide? [closed]

  - by smp7d

  At my company, the programmers who sit in the same area are constantly fighting over whether the lights stay on or off. Because there is no official policy it makes it a particularly sticky situation. We are a typical cube-farm and we have those typical cube-farm fluorescent lights and smaller ones at our desks. With the lights off, it is difficult to read and you would probably need to turn on your desk light (which some people do anyway). All programmers in our department do most of their reading on their monitor because of the nature of our business. Some feel that we should have a vote to decide whether the lights stay on or off. A couple who prefer 'lights on' feel that the vote would need to be unanimous to turn them off as having them on is the more natural office setting. Those who want them off point out that all other departments keep their lights off. I have heard all of the arguments: -Fluorescent lights cause eye strain -Reading in dark causes eye strain -The desk lights can be used if light is needed -People from other departments feel uncomfortable approaching us in the "dark" -The monitors are harder to see in the light ... Right now, some of the developers turn off the lights and some turn them on. It really just depends who last walked by the switch. I am a bit sick of the controversy as it feels a bit childish at the moment. I'm tired of hearing about it and I'm tired of having to talk about it. I tried to help them decide but as I explained, voting wasn't enough. Do other programming departments have this same argument? What is the standard or traditionally accepted option in a programming area? Are there any good reasons for one way or the other outside of preference? How can we decide fairly? EDIT Just a little more info... We do not have clients/visitors come into our office. We do have windows and hall lights that make our environment plenty bearable with the lights off. It kind of resembles a meeting room that has the lights off during a powerpoint presentation.

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• How to write comments to explain the "why" behind the callback function when the function and parameter names are insufficient for that?

  - by snowmantw

  How should I approach writing comments for callback functions? I want to explain the "why" behind the function when the function and parameter names are insufficient to explain what's going on. I have always wonder why comments like this can be so ordinary in documents of libraries in dynamic languages: /** * cb: callback // where's the arguments & effects? */ func foo( cb ) Maybe the common attitude is "you can look into source code on your own after all" which pushes people into leaving minimalist comments like this. But it seems like there should be a better way to comment callback functions. I've tried to comment callbacks in Haskell way: /** * cb: Int -> Char */ func foo(cb) And to be fair, it's usually neat enough. But it gets into trouble when I need to pass some complex structure. The problem being partly due to the lack of type system: /** * cb: Int -> { err: String -> (), success: () -> Char } // too long... */ func foo(cb) Or I have tried this too: /** * cb: Int -> { err: String -> (), * success: () -> Char } // better ? */ func bar(cb) The problem is that you may put the structure in somewhere else, but you must give it a name to reference it. But then when you name a structure you're about to use immediately looks so redundant: // Somewhere else... // ResultCallback: { err: String -> (), success: () -> Char } /** * cb: Int -> ResultCallback // better ?? */ func foo(cb) And it bothers me if I follow the Java-doc like commenting style since it still seems incomplete. The comments don't tell you anything that you couldn't immediately see from looking at the function. /** * @param cb {Function} yeah, it's a function, but you told me nothing about it... * @param err {Function} where should I put this callback's argument ?? * Not to mention the err's own arguments... */ func foo(cb) These examples are JavaScript like with generic functions and parameter names, but I've encountered similar problems in other dynamic languages which allow complex callbacks.

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