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  • What's a good Java-based Master-Slave communication mechanism?

    - by plecong
    I'm creating a Java application that requires master-slave communication between JVMs, possibly residing on the same physical machine. There will be a "master" server running inside a JEE application server (i.e. JBoss) that will have "slave" clients connect to it and dynamically register itself for communication (that is the master will not know the IP addresses/ports of the slaves so cannot be configured in advance). The master server acts as a controller that will dole work out to the slaves and the slaves will periodically respond with notifications, so there would be bi-directional communication. I was originally thinking of RPC-based systems where each side would be a server, but it could get complicated, so I'd prefer a mechanism where there's an open socket and they talk back and forth. I'm looking for a communication mechanism that would be low-latency where the messages would be mostly primitive types, so no serious serialization is necessary. Here's what I've looked at: RMI JMS: Built-in to Java, the "slave" clients would connect to the existing ConnectionFactory in the application server. JAX-WS/RS: Both master and slave would be servers exposing an RPC interface for bi-directional communication. JGroups/Hazelcast: Use shared distributed data structures to facilitate communication. Memcached/MongoDB: Use these as "queues" to facilitate communication, though the clients would have to poll so there would be some latency. Thrift: This does seem to keep a persistent connection, but not sure how to integrate/embed a Thrift server into JBoss WebSocket/Raw Socket: This would work, but require a lot more custom code than I'd like. Is there any technology I'm missing? Edit: Also looked at: JMX: Have the client connect to JBoss' JMX server and receive JMX notifications for bidirectional comms.

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  • How can I get the rank of rows relative to total number of rows based on a field?

    - by Arms
    I have a scores table that has two fields: user_id score I'm fetching specific rows that match a list of user_id's. How can I determine a rank for each row relative to the total number of rows, based on score? The rows in the result set are not necessarily sequential (the scores will vary widely from one row to the next). I'm not sure if this matters, but user_id is a unique field. Edit @Greelmo I'm already ordering the rows. If I fetch 15 rows, I don't want the rank to be 1-15. I need it to be the position of that row compared against the entire table by the score property. So if I have 200 rows, one row's rank may be 3 and another may be 179 (these are arbitrary #'s for example only). Edit 2 I'm having some luck with this query, but I actually want to avoid ties SELECT s.score , s.created_at , u.name , u.location , u.icon_id , u.photo , (SELECT COUNT(*) + 1 FROM scores WHERE score > s.score) AS rank FROM scores s LEFT JOIN users u ON u.uID = s.user_id ORDER BY s.score DESC , s.created_at DESC LIMIT 15 If two or more rows have the same score, I want the latest one (or earliest - I don't care) to be ranked higher. I tried modifying the subquery with AND id > s.id but that ended up giving me an unexpected result set and different ties.

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  • How do I relate two models/tables in Django based on non primary non unique keys?

    - by wizard
    I've got two tables that I need to relate on a single field po_num. The data is imported from another source so while I have a little bit of control over what the tables look like but I can't change them too much. What I want to do is relate these two models so I can look up one from the other based on the po_num fields. What I really need to do is join the two tables so I can do a where on a count of the related table. I would like to do filter for all Order objects that have 0 related EDI856 objects. I tried adding a foreign key to the Order model and specified the db_column and to_fields as po_num but django didn't like that the fact that Edi856.po_num wasn't unique. Here are the important fields of my current models that let me display but not filter for the data that I want. class Edi856(models.Model): po_num = models.CharField(max_length=90, db_index=True ) class Order(models.Model): po_num = models.CharField(max_length=90, db_index=True) def in_edi(self): '''Has the edi been processed?''' return Edi856.objects.filter(po_num = self.po_num).count() Thanks for taking the time to read about my problem. I'm not sure what to do from here.

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  • MS Acess SQL - where clause to get year from date based on the year - data located in MS access form

    - by primus285
    OK, back again. I have a problem getting a drop down list to populate based on information in two fields. I have got the SQL correct as to Select just one year if I put DateValue('01/01/2001') in both places, but I am trying now to get it to grab the year data from the MS access form - another drop down named "cboYear". I'd hate to have to do something in VB, unless necessary. so far I have gotten this to pull up something (its always incorrect) SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE Database_New.Date>=DateValue('01/01/' & [cboYear]) And Database_New.Date<=DateValue('12/31/' & [cboYear]); and SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE Database_New.Date>=DateValue('01/01/' + [cboYear]) And Database_New.Date<=DateValue('12/31/' + [cboYear]); SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE Database_New.Date>=DateValue('01/01/' AND [cboYear]) And Database_New.Date<=DateValue('12/31/' AND [cboYear]); both give errors saying that it is too complex to compute. Its probably something simple, but where do I go from here?

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  • How can I change the tags/css class of some dynamic text based on output from a helper?

    - by Angela
    I have a repeated line which outputs something like: Call John Jones in -3 days (status) I have a helper called show_status(contact,email) which will output whether that particular email had been sent to that particular contact. If it is "sent," then that entire line should show up as "strike out." Similarly, if the number of days is -3 (<0), the line should be formatted in red. Here's my hack, but there must be a cleaner way to put the logic into the controller? I hard-code a value that wraps around the lines I want formatted, and assign the value based on a separate call to the same helper: <% for call in @campaign.calls %> <% if !show_call_status(@contact,call).blank? %> <%= strike_start = '<s>'%> <%= strike_end = '</s>' %> <% end %> <p> <%= strike_start %> <%= link_to call.title, call_path(call) %> on <%= (@contact.date_entered + call.days).to_s(:long) %> in <%= interval_email(@contact,call) %> days <%= make_call(@contact,call) %> <span class='status'><%= show_call_status(@contact,call) %></span> <%= strike_end %> </p> <% end %> I guess what I'd like to do is not have the if statement in the View. Not sure how to do this.

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  • Pop-up and font colour based problems in a form which is designed in Share Point.

    - by ephieste
    I am designing a system in Share Point via Share Point Designer. We have a form in my Share Point site. Users have to fill some fields in the form and send it to the approval committee. We cannot upload anything to the servers. The design is site based. Our problems are: 1- I want to add small (?) icons for the descriptions of that field. When the user click on the (?) icon for "brief description" field a pop-up or another window will be opened and perhaps it will say: Enter a description of the requested thing. Be as specific as possible. 2- I want to change the font colors of the fields in the form. The share point brings them black as default. Such as I want to see the "Brief description:" and "Status:" as purple instead of black. Brief description: ..... Status: ..... 3- I want to add an agreement pop-up to the new form which will be open just after clicking "send" button in the form. The pop up will say: "Are you sure that you read the procedure" . The user has to click "Yes" to continue sending the form. Otherwise It will return to previous screen again. I would be glad if you kindly help me.

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  • jQuery Looking for a function to equalize heights of divs based on tallest image in a table.

    - by Jamie
    I am doing a site that will have a table with a bunch of images in them. They are user added images so I have no control over aspect ratio, what I do have control over is I can the force a max height/width and the image will not exceed this in either direction, but the height can (and will) fluctuate. <table class="pl_upload"> <tr class="row1"> <td class="col1"> <div> <div class="img-container"> <a href="#"><img src="img.jpg" width="182" alt="X" /></a> </div> </div> </td> ....... What I need ideally is to get the height of the tallest image and then make the all of the children divs the same height based on the height of the tallest one. I hope that makes sense, been a long day. I made a jsfiddle page for it here: http://jsfiddle.net/Evolution/27EJB/

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  • How to round-off hours based on Minutes(hours+0 if min<30, hours+1 otherwise) ?

    - by infant programmer
    I need to round-off the hours based on the minutes in a DateTime variable. The condition is: if minutes are less than 30, then minutes must be set to zero and no changes to hours, else if minutes =30, then hours must be set to hours+1 and minutes are again set to zero. Seconds are ignored. example: 11/08/2008 04:30:49 should become 11/08/2008 05:00:00 and 11/08/2008 04:29:49 should become 11/08/2008 04:00:00 I have written code which works perfectly fine, but just wanted to know a better method if could be written and also would appreciate alternative method(s). string date1 = "11/08/2008 04:30:49"; DateTime startTime; DateTime.TryParseExact(date1, "MM/dd/yyyy HH:mm:ss", null, System.Globalization.DateTimeStyles.None, out startTime); if (Convert.ToInt32((startTime.Minute.ToString())) > 29) { startTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}:{5}", startTime.Month.ToString(), startTime.Day.ToString(), startTime.Year.ToString(), startTime.Hour.ToString(), "00", "00")); startTime = startTime.Add(TimeSpan.Parse("01:00:00")); Console.WriteLine("startTime is :: {0}", startTime.ToString("MM/dd/yyyy HH:mm:ss")); } else { startTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}:{5}", startTime.Month.ToString(), startTime.Day.ToString(), startTime.Year.ToString(), startTime.Hour.ToString(), "00", "00")); Console.WriteLine("startTime is :: {0}", startTime.ToString("MM/dd/yyyy HH:mm:ss")); }

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  • How would a user stay logged in to a REST-based website?

    - by unforgiven3
    A year or so ago I asked this question: Can you help me understand this? “Common REST Mistakes: Sessions are irrelevant”. My question was essentially this: Okay, I get that HTTP authentication is done automatically on every message - but how? Is the username/password sent with every request? Doesn't that just increase attack surface area? I feel like I'm missing part of the puzzle. The answers I received made perfect sense in the context of a mobile (iPhone, Android, WP7) app - when talking to a REST service, the app would just send user credentials along with each request. That worked great for me. But now, I would like to better understand how one would secure a REST-like website, like StackOverflow itself or something like Reddit. How would things work if it was a user logged in via a web browser instead of logged in via an iPhone app? What happens when a user logs in? Are the credentials saved in the browser somehow? How would the browser know what credentials to send with subsequent REST requests? What if it's a JavaScript call to a webservice? How would the JavaScript call include user credentials? I'll be quite frank: my understanding of security when it comes to websites is pretty limited. I enjoyed working with REST services from an app perspective, but now I want to try and build a website that is based on REST principles, and I'm finding myself to be pretty lost. If there is anything in the above question that is unclear that you'd like me to clarify, please leave a comment and I'll address it.

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  • How to disable a checkbox based on date using php?

    - by udaya
    I have iterated a table based on my query result... I have a column lastDate it contains a date value like 01/24/2010... Now i have to check the date value with the current date if currentdate is less than or equal to lastDate i have to enable the checkbox else disable it..... Any suggestion how it can be done in php... Here is my code <? if(isset($comment)) { echo '<tr><td class=table_label colspan=5>'.$comment.'</td></tr>'; } ?> <td align="center" class="table_label" id="txtsubdat"> <? $dd=$row['dDate']; if($dd=='') { } else { $str = $dd; $dd = strtotime ( $str ); echo date ( 'm/d/Y' , $dd ); } ?> </td> <td align="center"> <input type="checkbox" name="group" id="group" value="<?=$row['dAssignment_id']?>" onclick="checkdisplay(this);"> </td> <? } ?>

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  • MySQL: How to pull information from multiple tables based on information in other tables?

    - by Greg
    Ok, I have 5 tables which I need to pull information from based on one variable. gameinfo id | name | platforminfoid gamerinfo id | name | contact | tag platforminfo id | name | abbreviation rosterinfo id | name | gameinfoid rosters id | gamerinfoid | rosterinfoid The 1 variable would be gamerinfo.id, which would then pull all relevant data from gamerinfo, which would pull all relevant data from rosters, which would pull all relevant data from rosterinfo, which would pull all relevant data from gameinfo, which would then pull all relevant data from platforminfo. Basically it breaks down like this: gamerinfo contains the gamers basic information. rosterinfo contains basic information about the rosters (ie name and the game the roster is aimed towards) rosters contains the actual link from the gamer to the different rosters (gamers can be on multiple rosters) gameinfo contains basic information about the games (ie name and platform) platform info contains information about the different platforms the games are played on (it is possible for a game to be played on multiple platforms) I am pretty new to SQL queries involving JOINs and UNIONs and such, usually I would just break it up into multiple queries but I thought there has to be a better way, so after looking around the net, I couldn't find (or maybe I just couldn't understand what I was looking at) what I was looking for. If anyone can point me in the right direction I would be most grateful.

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  • How to alter Postgres table data based on its contents?

    - by williamjones
    This is probably a super simple question, but I'm struggling to come up with the right keywords to find it on Google. I have a Postgres table that has among its contents a column of type text named content_type. That stores what type of entry is stored in that row. There are only about 5 different types, and I decided I want to change one of them to display as something else in my application (I had been directly displaying these). It struck me that it's funny that my view is being dictated by my database model, and I decided I would convert the types being stored in my database as strings into integers, and enumerate the possible types in my application with constants that convert them into their display names. That way, if I ever got the urge to change any category names again, I could just change it with one alteration of a constant. I also have the hunch that storing integers might be somewhat more efficient than storing text in the database. First, a quick threshold question of, is this a good idea? Any feedback or anything I missed? Second, and my main question, what's the Postgres command I could enter to make an alteration like this? I'm thinking I could start by renaming the old content_type column to old_content_type and then creating a new integer column content_type. However, what command would look at a row's old_content_type and fill in the new content_type column based off of that?

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  • Looking for an issue tracker / project management software that automatically manages start/completion dates based on priority/relationships

    - by user361910
    So, a little background. We are a small company with a half-dozen developers. We have been evaluating many project management / issue tracking software packages (TRAC, Redmine, FogBugz, etc) and trying to create a decent process/workflow for managing projects, adding features, fixing bugs, etc. I'd like to think our requirements are similar to most other companies our size. Essentially, what this comes down to is 1) An easy way for the PM and developers to track projects, issues, bugs, etc 2) An easy way for the PM and admin/executives to get a birds-eye view of progress and easily manage timelines, schedules, and priorities. After trying TRAC, we moved to Redmine. We found Redmine to be easier than track to administer and the ability to have sub-projects and sub-tickets is great. However, the big problem we ran into is the fact that it is very difficult to manage schedules and timelines. It seems like it would be incredibly time-intensive to manage because you have to manually enter a start date, estimated time, and end date for each ticket, project, etc. So if you setup a month's schedule based on priorities, what are you supposed to do when a particular ticket/issue/subproject takes up more time than was estimated. Right now, it appears I would have to go back in and MANUALLY change the start/end date of every single item. What would be ideal is to be able to set priorities/dependencies and estimated time on tickets/milestones, and have the software automatically manage the start/end dates. Does anyone know how to get Redmine to do this, or recommend a different software package that can do something like this!

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  • C# : How to round-off hours based on Minutes(hours+0 if min<30, hours+1 otherwise) ?

    - by infant programmer
    I need to round-off the hours based on the minutes in a dateTime variable. The condition is : if minutes are less than 30, then minutes must be set to zero and no changes to hours, Else if minutes =30, then hours must be set to hours+1 and minutes are again set to zero. Seconds are ignored. example: 11/08/2008 04:30:49 should become 11/08/2008 05:00:00 and 11/08/2008 04:29:49 should become 11/08/2008 04:00:00 I have written a Code which works perfectly fine, but just wanted to know a better method if could be written and also would appreciate alternative method(s). string date1 = "11/08/2008 04:30:49"; DateTime startTime; DateTime.TryParseExact(date1, "MM/dd/yyyy HH:mm:ss", null, System.Globalization.DateTimeStyles.None, out startTime); if (Convert.ToInt32((startTime.Minute.ToString())) > 29) { startTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}:{5}", startTime.Month.ToString(), startTime.Day.ToString(), startTime.Year.ToString(), startTime.Hour.ToString(), "00", "00")); startTime = startTime.Add(TimeSpan.Parse("01:00:00")); Console.WriteLine("startTime is :: {0}", startTime.ToString("MM/dd/yyyy HH:mm:ss")); } else { startTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}:{5}", startTime.Month.ToString(), startTime.Day.ToString(), startTime.Year.ToString(), startTime.Hour.ToString(), "00", "00")); Console.WriteLine("startTime is :: {0}", startTime.ToString("MM/dd/yyyy HH:mm:ss")); }

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  • PHP-How to choose XML section based on an attribute?

    - by Vincent
    All, I have a config xml file in the following format: <?xml version="1.0"?> <configdata> <development> <siteTitle>You are doing Development</siteTitle> </development> <test extends="development"> <siteTitle>You are doing Testing</siteTitle> </test> <production extends="development"> <siteTitle>You are in Production</siteTitle> </production> </configdata> To read this config file to apply environment settings, currently I am using, the following code in index.php file: $appEnvironment = "production"; $config = new Zend_Config_Xml('/config/settings.xml', $appEnvironment ); To deploy this code on multiple environments, as user has to change index.php file. Instead of doing that, is it possible to maintain an attribute in the xml file, "say active=true". Based on which the Zend_Config_Xml will know which section of the xml file settings to read? Thanks

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  • How to: StructureMap and configuration based on runtime parameters?

    - by user981375
    In a nutshell - I want to be able to instantiate object based on runtime parameters. In this particular case there are only two parameters but the problem is that I'm facing different permutations of these parameters and it gets messy. Here is the situation: I want to get an instance of an object specific to, say, given country and then, say, specific state/province. So, considering the US, there are 50 possible combinations. In reality it's less than that but that's the max. Think of it this way, I want to find out what's the penalty for smoking pot in a given country/state, I pass this information in and I get instantiated object telling me what it is. To the code (for reference only): interface IState { string Penalty { get; } } interface ICountry { IState State { get; set; } string Name { get; } } class BasePenalty : IState { virtual public string Penalty { get { return "Slap on a wrist"; } } } class USA : ICountry { public USA(IState state) { State = state; } public IState State { get; set; } public string Name { get { return "USA"; } } } class Florida: BasePenalty { public override string Penalty { get { return "Public beheading"; } } } // and so on ... I defined other states // which have penalties other than the "Slap on a wrist" How do I configure my container that when given country and state combination it will return the penalty? I tried combinations of profile and contextual binding but that configuration was directly proportional to the number of classes I've created. I have already gone thru trouble of defining different combinations. I'd like to avoid having to do the same during container configuration. I want to inject State into the Country. Also, I'd like to return UsaBasePenalty value in case state is not specified. Is that possible? Perhaps these is something wrong with the design.

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  • Is there a set based solution for this problem?

    - by NYSystemsAnalyst
    We have a table set up as follows: |ID|EmployeeID|Date |Category |Hours| |1 |1 |1/1/2010 |Vacation Earned|2.0 | |2 |2 |2/12/2010|Vacation Earned|3.0 | |3 |1 |2/4/2010 |Vacation Used |1.0 | |4 |2 |5/18/2010|Vacation Earned|2.0 | |5 |2 |7/23/2010|Vacation Used |4.0 | The business rules are: Vacation balance is calculated by vacation earned minus vacation used. Vacation used is always applied against the oldest vacation earned amount first. We need to return the rows for Vacation Earned that have not been offset by vacation used. If vacation used has only offset part of a vacation earned record, we need to return that record showing the difference. For example, using the above table, the result set would look like: |ID|EmployeeID|Date |Category |Hours| |1 |1 |1/1/2010 |Vacation Earned|1.0 | |4 |2 |5/18/2010|Vacation Earned|1.0 | Note that record 2 was eliminated because it was completely offset by used time, but records 1 and 4 were only partially used, so they were calculated and returned as such. The only way we have thought of to do this is to get all of the vacation earned records in a temporary table. Then, get the total vacation used and loop through the temporary table, deleting the oldest record and subtracting that value from the total vacation used until the total vacation used is zero. We could clean it up for when the remaining vacation used is only part of the oldest vacation earned record. This would leave us with just the outstanding vacation earned records. This works, but it is very inefficient and performs poorly. Also, the performance will just degrade over time as more and more records are added. Are there any suggestions for a better solution, preferable set based? If not, we'll just have to go with this.

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  • How to further improve error messages in Scala parser-combinator based parsers?

    - by rse
    I've coded a parser based on Scala parser combinators: class SxmlParser extends RegexParsers with ImplicitConversions with PackratParsers { [...] lazy val document: PackratParser[AstNodeDocument] = ((procinst | element | comment | cdata | whitespace | text)*) ^^ { AstNodeDocument(_) } [...] } object SxmlParser { def parse(text: String): AstNodeDocument = { var ast = AstNodeDocument() val parser = new SxmlParser() val result = parser.parseAll(parser.document, new CharArrayReader(text.toArray)) result match { case parser.Success(x, _) => ast = x case parser.NoSuccess(err, next) => { tool.die("failed to parse SXML input " + "(line " + next.pos.line + ", column " + next.pos.column + "):\n" + err + "\n" + next.pos.longString) } } ast } } Usually the resulting parsing error messages are rather nice. But sometimes it becomes just sxml: ERROR: failed to parse SXML input (line 32, column 1): `"' expected but `' found ^ This happens if a quote characters is not closed and the parser reaches the EOT. What I would like to see here is (1) what production the parser was in when it expected the '"' (I've multiple ones) and (2) where in the input this production started parsing (which is an indicator where the opening quote is in the input). Does anybody know how I can improve the error messages and include more information about the actual internal parsing state when the error happens (perhaps something like a production rule stacktrace or whatever can be given reasonably here to better identify the error location). BTW, the above "line 32, column 1" is actually the EOT position and hence of no use here, of course.

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  • A data structure based on the R-Tree: creating new child nodes when a node is full, but what if I ha

    - by Tom
    I realize my title is not very clear, but I am having trouble thinking of a better one. If anyone wants to correct it, please do. I'm developing a data structure for my 2 dimensional game with an infinite universe. The data structure is based on a simple (!) node/leaf system, like the R-Tree. This is the basic concept: you set howmany childs you want a node (a container) to have maximum. If you want to add a leaf, but the node the leaf should be in is full, then it will create a new set of nodes within this node and move all current leafs to their new (more exact) node. This way, very populated areas will have a lot more subdivisions than a very big but rarely visited area. This works for normal objects. The only problem arises when I have more than maxChildsPerNode objects with the exact same X,Y location: because the node is full, it will create more exact subnodes, but the old leafs will all be put in the exact same node again because they have the exact same position -- resulting in an infinite loop of creating more nodes and more nodes. So, what should I do when I want to add more leafs than maxChildsPerNode with the exact same position to my tree? PS. if I failed to explain my problem, please tell me, so I can try to improve the explanation.

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  • How can I set paperclip's storage mechanism based on the current Rails environment?

    - by John Reilly
    I have a rails application that has multiple models with paperclip attachments that are all uploaded to S3. This app also has a large test suite that is run quite often. The downside with this is that a ton of files are uploaded to our S3 account on every test run, making the test suite run slowly. It also slows down development a bit, and requires you to have an internet connection in order to work on the code. Is there a reasonable way to set the paperclip storage mechanism based on the Rails environment? Ideally, our test and development environments would use the local filesystem storage, and the production environment would use S3 storage. I'd also like to extract this logic into a shared module of some kind, since we have several models that will need this behavior. I'd like to avoid a solution like this inside of every model: ### We don't want to do this in our models... if Rails.env.production? has_attached_file :image, :styles => {...}, :storage => :s3, # ...etc... else has_attached_file :image, :styles => {...}, :storage => :filesystem, # ...etc... end Any advice or suggestions would be greatly appreciated! :-)

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  • How can I have a Label change dynamically based on a Slider Value?

    - by duney
    I'm writing a grade calculator and I currently have a slider with a textbox beside it which displays the current value of the slider: <Slider Name="gradeSlider" Grid.Row="3" Grid.Column="2" VerticalAlignment="Center" Minimum="40" Maximum="100" IsSnapToTickEnabled="True" TickFrequency="5" TickPlacement="BottomRight"/> <TextBox Name="targetGrade" Grid.Row="3" Grid.Column="3" Width="30" Height="23" Text="{Binding ElementName=gradeSlider, Path=Value}" TextAlignment="Center"/> However I'm struggling to include a label which will show display a different grade classification based on the slider's value range. I'd have thought that I could create the label: <Label Name="gradeClass" Grid.Row="2" Grid.Column="2" HorizontalAlignment="Center" VerticalAlignment="Bottom"/> And then use code: string gradeText; if (gradeSlider.Value >= 40 && gradeSlider.Value < 50) { gradeText = "Pass"; gradeClass.Content = gradeText; } else if (gradeSlider.Value >= 50 && gradeSlider.Value < 60) { gradeText = "2:2"; gradeClass.Content = gradeText; } else { gradeText = "so on..."; gradeClass.Content = gradeText; } But the label just stays as "Pass" whatever the slider value. Could somebody please advise me as to where I'm going wrong? I tried using Content = "{Binding Source = gradeText}" on the Label xaml and removing the gradeClass.Content's in the code but it complained that gradeText was declared but never used. Many thanks to anyone who can help.

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  • Rails - HABTM Relationship -- How Can I Find A Record Based On An Attribute Of The Associated Model

    - by ChrisWesAllen
    I have setup this HABTM relationship in the past and its worked before....Now it isnt and I'm at my wits end trying to figure out whats wrong. I've looking through the rails guides all day and cant seem to figure out what I'm doing wrong, so help would really be appreciated. I have 2 models connected through a join model and I'm trying to find records based an attribute of the associated model. Event.rb has_and_belongs_to_many :interests Interest.rb has_and_belongs_to_many :events and a join table migration that was created like create_table 'events_interests', :id => false do |t| t.column :event_id, :integer t.column :interest_id, :integer end I tried @events = Event.all(:include => :interest, :conditions => [" interest.id = ?", 4 ] ) But got the error "Association named 'interest' was not found; perhaps you misspelled it?"... which I didnt of course I tried @events = Event.interests.find(:all, :conditions => [" interest.id = ?", 4 ] ) but got the error "undefined method `interests' for #Class:0x4383348" How can I find the Events that have an interest id of 4....I'm definitely going bald from this lol

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  • What kind of online hosting do I need for a WCF-based service?

    - by mafutrct
    First of all, I'm not sure if SO is the right place to ask. Please migrate me if needed. I would like to host a WCF-based service so it is available for everyone. While hosting it on my personal, local servers succeeded, I would prefer to move it to an external service provider for various reasons. I'll be blunt: I have no clue about hosting providers. I know there are webhosters, virtual and root servers and several other services. What I would like to know is what kind of hosting I need in my case. I understand that a root server would easily fulfill my requirements, but that is not exactly cheap. The program I'd like to run on the server requires .NET 4, preferably on a windows machine. Access to a folder in the file system is much appreciated (1 GB storage is enough by far). Communication with clients (in form of an applications written in .NET) via opening a port on the server. Traffic is low (<<1 GB/month?) There is no website. Having the provider perform updates would be nice. My understanding is that a virtual server would be a possible solution. Prices seem start at around 5€/month, which is ok for me. However, I read that for these cheap solutions RAM is severely limited (~400 MB), and I'm not confident that is enough to run windows and a .NET application.

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  • EDIT: I need to generate a string of 7 chars that is based on the id of the row.

    - by Totty
    EDIT: I need to generate a string of 7 chars that is based on the id of the row. So knowing the id of the image and a secret key, i should get the generated string. the string must contain chars from "a" to "z" and numbers from 0 to 9. I have a dir that contains photos like this dir/p3/i2/s21/thumb.jpg the generated string is p3i2s21, then is used to calculate the path of the image. EDIT: currently im using the id of the image: id = 55 then i modify and i get path = 000000055 then path = "000/000/055" then path = "000/000/055/thumb.jpg" ready to use! now i want something more clever because is easy to track down all the images from a server, because ids are sequencial: 1, 2, 3, 4, 5, 6... so i must think of creating from 55 a string that is 7 char length and will not overlap with other numbers. I can even transform the 55 to 0000055 and from this convert to a 7 char length string using a secret string. then when i got the secret string and the id i want to get back that 7 char length string. Is this possible? i was thinking about hases but they only uses 0-9 and a-e and are more chars.. :s

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  • The broken Promise of the Mobile Web

    - by Rick Strahl
    High end mobile devices have been with us now for almost 7 years and they have utterly transformed the way we access information. Mobile phones and smartphones that have access to the Internet and host smart applications are in the hands of a large percentage of the population of the world. In many places even very remote, cell phones and even smart phones are a common sight. I’ll never forget when I was in India in 2011 I was up in the Southern Indian mountains riding an elephant out of a tiny local village, with an elephant herder in front riding atop of the elephant in front of us. He was dressed in traditional garb with the loin wrap and head cloth/turban as did quite a few of the locals in this small out of the way and not so touristy village. So we’re slowly trundling along in the forest and he’s lazily using his stick to guide the elephant and… 10 minutes in he pulls out his cell phone from his sash and starts texting. In the middle of texting a huge pig jumps out from the side of the trail and he takes a picture running across our path in the jungle! So yeah, mobile technology is very pervasive and it’s reached into even very buried and unexpected parts of this world. Apps are still King Apps currently rule the roost when it comes to mobile devices and the applications that run on them. If there’s something that you need on your mobile device your first step usually is to look for an app, not use your browser. But native app development remains a pain in the butt, with the requirement to have to support 2 or 3 completely separate platforms. There are solutions that try to bridge that gap. Xamarin is on a tear at the moment, providing their cross-device toolkit to build applications using C#. While Xamarin tools are impressive – and also *very* expensive – they only address part of the development madness that is app development. There are still specific device integration isssues, dealing with the different developer programs, security and certificate setups and all that other noise that surrounds app development. There’s also PhoneGap/Cordova which provides a hybrid solution that involves creating local HTML/CSS/JavaScript based applications, and then packaging them to run in a specialized App container that can run on most mobile device platforms using a WebView interface. This allows for using of HTML technology, but it also still requires all the set up, configuration of APIs, security keys and certification and submission and deployment process just like native applications – you actually lose many of the benefits that  Web based apps bring. The big selling point of Cordova is that you get to use HTML have the ability to build your UI once for all platforms and run across all of them – but the rest of the app process remains in place. Apps can be a big pain to create and manage especially when we are talking about specialized or vertical business applications that aren’t geared at the mainstream market and that don’t fit the ‘store’ model. If you’re building a small intra department application you don’t want to deal with multiple device platforms and certification etc. for various public or corporate app stores. That model is simply not a good fit both from the development and deployment perspective. Even for commercial, big ticket apps, HTML as a UI platform offers many advantages over native, from write-once run-anywhere, to remote maintenance, single point of management and failure to having full control over the application as opposed to have the app store overloads censor you. In a lot of ways Web based HTML/CSS/JavaScript applications have so much potential for building better solutions based on existing Web technologies for the very same reasons a lot of content years ago moved off the desktop to the Web. To me the Web as a mobile platform makes perfect sense, but the reality of today’s Mobile Web unfortunately looks a little different… Where’s the Love for the Mobile Web? Yet here we are in the middle of 2014, nearly 7 years after the first iPhone was released and brought the promise of rich interactive information at your fingertips, and yet we still don’t really have a solid mobile Web platform. I know what you’re thinking: “But we have lots of HTML/JavaScript/CSS features that allows us to build nice mobile interfaces”. I agree to a point – it’s actually quite possible to build nice looking, rich and capable Web UI today. We have media queries to deal with varied display sizes, CSS transforms for smooth animations and transitions, tons of CSS improvements in CSS 3 that facilitate rich layout, a host of APIs geared towards mobile device features and lately even a number of JavaScript framework choices that facilitate development of multi-screen apps in a consistent manner. Personally I’ve been working a lot with AngularJs and heavily modified Bootstrap themes to build mobile first UIs and that’s been working very well to provide highly usable and attractive UI for typical mobile business applications. From the pure UI perspective things actually look very good. Not just about the UI But it’s not just about the UI - it’s also about integration with the mobile device. When it comes to putting all those pieces together into what amounts to a consolidated platform to build mobile Web applications, I think we still have a ways to go… there are a lot of missing pieces to make it all work together and integrate with the device more smoothly, and more importantly to make it work uniformly across the majority of devices. I think there are a number of reasons for this. Slow Standards Adoption HTML standards implementations and ratification has been dreadfully slow, and browser vendors all seem to pick and choose different pieces of the technology they implement. The end result is that we have a capable UI platform that’s missing some of the infrastructure pieces to make it whole on mobile devices. There’s lots of potential but what is lacking that final 10% to build truly compelling mobile applications that can compete favorably with native applications. Some of it is the fragmentation of browsers and the slow evolution of the mobile specific HTML APIs. A host of mobile standards exist but many of the standards are in the early review stage and they have been there stuck for long periods of time and seem to move at a glacial pace. Browser vendors seem even slower to implement them, and for good reason – non-ratified standards mean that implementations may change and vendor implementations tend to be experimental and  likely have to be changed later. Neither Vendors or developers are not keen on changing standards. This is the typical chicken and egg scenario, but without some forward momentum from some party we end up stuck in the mud. It seems that either the standards bodies or the vendors need to carry the torch forward and that doesn’t seem to be happening quickly enough. Mobile Device Integration just isn’t good enough Current standards are not far reaching enough to address a number of the use case scenarios necessary for many mobile applications. While not every application needs to have access to all mobile device features, almost every mobile application could benefit from some integration with other parts of the mobile device platform. Integration with GPS, phone, media, messaging, notifications, linking and contacts system are benefits that are unique to mobile applications and could be widely used, but are mostly (with the exception of GPS) inaccessible for Web based applications today. Unfortunately trying to do most of this today only with a mobile Web browser is a losing battle. Aside from PhoneGap/Cordova’s app centric model with its own custom API accessing mobile device features and the token exception of the GeoLocation API, most device integration features are not widely supported by the current crop of mobile browsers. For example there’s no usable messaging API that allows access to SMS or contacts from HTML. Even obvious components like the Media Capture API are only implemented partially by mobile devices. There are alternatives and workarounds for some of these interfaces by using browser specific code, but that’s might ugly and something that I thought we were trying to leave behind with newer browser standards. But it’s not quite working out that way. It’s utterly perplexing to me that mobile standards like Media Capture and Streams, Media Gallery Access, Responsive Images, Messaging API, Contacts Manager API have only minimal or no traction at all today. Keep in mind we’ve had mobile browsers for nearly 7 years now, and yet we still have to think about how to get access to an image from the image gallery or the camera on some devices? Heck Windows Phone IE Mobile just gained the ability to upload images recently in the Windows 8.1 Update – that’s feature that HTML has had for 20 years! These are simple concepts and common problems that should have been solved a long time ago. It’s extremely frustrating to see build 90% of a mobile Web app with relative ease and then hit a brick wall for the remaining 10%, which often can be show stoppers. The remaining 10% have to do with platform integration, browser differences and working around the limitations that browsers and ‘pinned’ applications impose on HTML applications. The maddening part is that these limitations seem arbitrary as they could easily work on all mobile platforms. For example, SMS has a URL Moniker interface that sort of works on Android, works badly with iOS (only works if the address is already in the contact list) and not at all on Windows Phone. There’s no reason this shouldn’t work universally using the same interface – after all all phones have supported SMS since before the year 2000! But, it doesn’t have to be this way Change can happen very quickly. Take the GeoLocation API for example. Geolocation has taken off at the very beginning of the mobile device era and today it works well, provides the necessary security (a big concern for many mobile APIs), and is supported by just about all major mobile and even desktop browsers today. It handles security concerns via prompts to avoid unwanted access which is a model that would work for most other device APIs in a similar fashion. One time approval and occasional re-approval if code changes or caches expire. Simple and only slightly intrusive. It all works well, even though GeoLocation actually has some physical limitations, such as representing the current location when no GPS device is present. Yet this is a solved problem, where other APIs that are conceptually much simpler to implement have failed to gain any traction at all. Technically none of these APIs should be a problem to implement, but it appears that the momentum is just not there. Inadequate Web Application Linking and Activation Another important piece of the puzzle missing is the integration of HTML based Web applications. Today HTML based applications are not first class citizens on mobile operating systems. When talking about HTML based content there’s a big difference between content and applications. Content is great for search engine discovery and plain browser usage. Content is usually accessed intermittently and permanent linking is not so critical for this type of content.  But applications have different needs. Applications need to be started up quickly and must be easily switchable to support a multi-tasking user workflow. Therefore, it’s pretty crucial that mobile Web apps are integrated into the underlying mobile OS and work with the standard task management features. Unfortunately this integration is not as smooth as it should be. It starts with actually trying to find mobile Web applications, to ‘installing’ them onto a phone in an easily accessible manner in a prominent position. The experience of discovering a Mobile Web ‘App’ and making it sticky is by no means as easy or satisfying. Today the way you’d go about this is: Open the browser Search for a Web Site in the browser with your search engine of choice Hope that you find the right site Hope that you actually find a site that works for your mobile device Click on the link and run the app in a fully chrome’d browser instance (read tiny surface area) Pin the app to the home screen (with all the limitations outline above) Hope you pointed at the right URL when you pinned Even for you and me as developers, there are a few steps in there that are painful and annoying, but think about the average user. First figuring out how to search for a specific site or URL? And then pinning the app and hopefully from the right location? You’ve probably lost more than half of your audience at that point. This experience sucks. For developers too this process is painful since app developers can’t control the shortcut creation directly. This problem often gets solved by crazy coding schemes, with annoying pop-ups that try to get people to create shortcuts via fancy animations that are both annoying and add overhead to each and every application that implements this sort of thing differently. And that’s not the end of it - getting the link onto the home screen with an application icon varies quite a bit between browsers. Apple’s non-standard meta tags are prominent and they work with iOS and Android (only more recent versions), but not on Windows Phone. Windows Phone instead requires you to create an actual screen or rather a partial screen be captured for a shortcut in the tile manager. Who had that brilliant idea I wonder? Surprisingly Chrome on recent Android versions seems to actually get it right – icons use pngs, pinning is easy and pinned applications properly behave like standalone apps and retain the browser’s active page state and content. Each of the platforms has a different way to specify icons (WP doesn’t allow you to use an icon image at all), and the most widely used interface in use today is a bunch of Apple specific meta tags that other browsers choose to support. The question is: Why is there no standard implementation for installing shortcuts across mobile platforms using an official format rather than a proprietary one? Then there’s iOS and the crazy way it treats home screen linked URLs using a crazy hybrid format that is neither as capable as a Web app running in Safari nor a WebView hosted application. Moving off the Web ‘app’ link when switching to another app actually causes the browser and preview it to ‘blank out’ the Web application in the Task View (see screenshot on the right). Then, when the ‘app’ is reactivated it ends up completely restarting the browser with the original link. This is crazy behavior that you can’t easily work around. In some situations you might be able to store the application state and restore it using LocalStorage, but for many scenarios that involve complex data sources (like say Google Maps) that’s not a possibility. The only reason for this screwed up behavior I can think of is that it is deliberate to make Web apps a pain in the butt to use and forcing users trough the App Store/PhoneGap/Cordova route. App linking and management is a very basic problem – something that we essentially have solved in every desktop browser – yet on mobile devices where it arguably matters a lot more to have easy access to web content we have to jump through hoops to have even a remotely decent linking/activation experience across browsers. Where’s the Money? It’s not surprising that device home screen integration and Mobile Web support in general is in such dismal shape – the mobile OS vendors benefit financially from App store sales and have little to gain from Web based applications that bypass the App store and the cash cow that it presents. On top of that, platform specific vendor lock-in of both end users and developers who have invested in hardware, apps and consumables is something that mobile platform vendors actually aspire to. Web based interfaces that are cross-platform are the anti-thesis of that and so again it’s no surprise that the mobile Web is on a struggling path. But – that may be changing. More and more we’re seeing operations shifting to services that are subscription based or otherwise collect money for usage, and that may drive more progress into the Web direction in the end . Nothing like the almighty dollar to drive innovation forward. Do we need a Mobile Web App Store? As much as I dislike moderated experiences in today’s massive App Stores, they do at least provide one single place to look for apps for your device. I think we could really use some sort of registry, that could provide something akin to an app store for mobile Web apps, to make it easier to actually find mobile applications. This could take the form of a specialized search engine, or maybe a more formal store/registry like structure. Something like apt-get/chocolatey for Web apps. It could be curated and provide at least some feedback and reviews that might help with the integrity of applications. Coupled to that could be a native application on each platform that would allow searching and browsing of the registry and then also handle installation in the form of providing the home screen linking, plus maybe an initial security configuration that determines what features are allowed access to for the app. I’m not holding my breath. In order for this sort of thing to take off and gain widespread appeal, a lot of coordination would be required. And in order to get enough traction it would have to come from a well known entity – a mobile Web app store from a no name source is unlikely to gain high enough usage numbers to make a difference. In a way this would eliminate some of the freedom of the Web, but of course this would also be an optional search path in addition to the standard open Web search mechanisms to find and access content today. Security Security is a big deal, and one of the perceived reasons why so many IT professionals appear to be willing to go back to the walled garden of deployed apps is that Apps are perceived as safe due to the official review and curation of the App stores. Curated stores are supposed to protect you from malware, illegal and misleading content. It doesn’t always work out that way and all the major vendors have had issues with security and the review process at some time or another. Security is critical, but I also think that Web applications in general pose less of a security threat than native applications, by nature of the sandboxed browser and JavaScript environments. Web applications run externally completely and in the HTML and JavaScript sandboxes, with only a very few controlled APIs allowing access to device specific features. And as discussed earlier – security for any device interaction can be granted the same for mobile applications through a Web browser, as they can for native applications either via explicit policies loaded from the Web, or via prompting as GeoLocation does today. Security is important, but it’s certainly solvable problem for Web applications even those that need to access device hardware. Security shouldn’t be a reason for Web apps to be an equal player in mobile applications. Apps are winning, but haven’t we been here before? So now we’re finding ourselves back in an era of installed app, rather than Web based and managed apps. Only it’s even worse today than with Desktop applications, in that the apps are going through a gatekeeper that charges a toll and censors what you can and can’t do in your apps. Frankly it’s a mystery to me why anybody would buy into this model and why it’s lasted this long when we’ve already been through this process. It’s crazy… It’s really a shame that this regression is happening. We have the technology to make mobile Web apps much more prominent, but yet we’re basically held back by what seems little more than bureaucracy, partisan bickering and self interest of the major parties involved. Back in the day of the desktop it was Internet Explorer’s 98+%  market shareholding back the Web from improvements for many years – now it’s the combined mobile OS market in control of the mobile browsers. If mobile Web apps were allowed to be treated the same as native apps with simple ways to install and run them consistently and persistently, that would go a long way to making mobile applications much more usable and seriously viable alternatives to native apps. But as it is mobile apps have a severe disadvantage in placement and operation. There are a few bright spots in all of this. Mozilla’s FireFoxOs is embracing the Web for it’s mobile OS by essentially building every app out of HTML and JavaScript based content. It supports both packaged and certified package modes (that can be put into the app store), and Open Web apps that are loaded and run completely off the Web and can also cache locally for offline operation using a manifest. Open Web apps are treated as full class citizens in FireFoxOS and run using the same mechanism as installed apps. Unfortunately FireFoxOs is getting a slow start with minimal device support and specifically targeting the low end market. We can hope that this approach will change and catch on with other vendors, but that’s also an uphill battle given the conflict of interest with platform lock in that it represents. Recent versions of Android also seem to be working reasonably well with mobile application integration onto the desktop and activation out of the box. Although it still uses the Apple meta tags to find icons and behavior settings, everything at least works as you would expect – icons to the desktop on pinning, WebView based full screen activation, and reliable application persistence as the browser/app is treated like a real application. Hopefully iOS will at some point provide this same level of rudimentary Web app support. What’s also interesting to me is that Microsoft hasn’t picked up on the obvious need for a solid Web App platform. Being a distant third in the mobile OS war, Microsoft certainly has nothing to lose and everything to gain by using fresh ideas and expanding into areas that the other major vendors are neglecting. But instead Microsoft is trying to beat the market leaders at their own game, fighting on their adversary’s terms instead of taking a new tack. Providing a kick ass mobile Web platform that takes the lead on some of the proposed mobile APIs would be something positive that Microsoft could do to improve its miserable position in the mobile device market. Where are we at with Mobile Web? It sure sounds like I’m really down on the Mobile Web, right? I’ve built a number of mobile apps in the last year and while overall result and response has been very positive to what we were able to accomplish in terms of UI, getting that final 10% that required device integration dialed was an absolute nightmare on every single one of them. Big compromises had to be made and some features were left out or had to be modified for some devices. In two cases we opted to go the Cordova route in order to get the integration we needed, along with the extra pain involved in that process. Unless you’re not integrating with device features and you don’t care deeply about a smooth integration with the mobile desktop, mobile Web development is fraught with frustration. So, yes I’m frustrated! But it’s not for lack of wanting the mobile Web to succeed. I am still a firm believer that we will eventually arrive a much more functional mobile Web platform that allows access to the most common device features in a sensible way. It wouldn't be difficult for device platform vendors to make Web based applications first class citizens on mobile devices. But unfortunately it looks like it will still be some time before this happens. So, what’s your experience building mobile Web apps? Are you finding similar issues? Just giving up on raw Web applications and building PhoneGap apps instead? Completely skipping the Web and going native? Leave a comment for discussion. Resources Rick Strahl on DotNet Rocks talking about Mobile Web© Rick Strahl, West Wind Technologies, 2005-2014Posted in HTML5  Mobile   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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