Search Results

Search found 7086 results on 284 pages for 'explain'.

Page 164/284 | < Previous Page | 160 161 162 163 164 165 166 167 168 169 170 171  | Next Page >

• What exactly is Two-way databinding in WPF ?

  - by blntechie

  I'm learning WPF with MVVM and for a starter, I viewed Jason Dolinger's video on MVVM . In that he mentioned, that one of the advantage of using MVVM with WPF is two-way data binding. My question is what does he mean by two-way data binding? Is that the feature of ability to 1) bind data from controls(View) to properties in VM and 2) any change in collections or properties are reflected in the view? If I'm wrong, can anyone please explain me in detail what it is and what are its advantages? This might be a very simple doubt, but I'm very new to WPF and it's terminologies and moving away from WinForms now.

  Read the article

• Rails: unexpected behavior updating a shared instance

  - by Pascal Lindelauf

  I have a User object, that is related to a Post object via two different association paths: Post --(has_many)-- comments --(belongs to)-- writer (of type User) Post --(belongs to)-- writer (of type User) Say the following hold: user1.name == "Bill" post1.comments[1].writer == user1 post1.writer == user1 Now when I retrieve the post1 and its comments from the database and I update post1.comments[1].writer like so: post1.comments[1].writer.name = "John" I would expect post1.writer to equal "John" too. But it doesn't! It still equals "Bill". So there seems to be some caching going on, but the kind I would not expect. I would expect Rails to be clever enough to load exactly one instance of the user with name "Bill"; instead is appears to load two individual ones: one for each association path. Can someone explain how this works exactly and how I am to handle these types of situations the "Rails way"?

  Read the article

• How extension methods work in background ?

  - by Freshblood

  I am just cuirous about behind of extension method mechanism.Some questions and answer appear in my mind. MyClass.OrderBy(x=>x.a).OrderBy(x=>x.b); I was guessing that mechanism was first orderby method works and order them by a member then returns sorted items in IEnumarable interface then next Orderby method of IEnumarable Order them for b paramater.But i am wrong when i look at this linq query. MyClass.Orderby(x=>x.a).ThenOrderBy(x=>x.b); this is slightly different and tells me that i am wrong.Because this is not ordering by a then b and not possible to have such result if i was right.This get me confuse enough... Similiar structure is possible to write withot extension methods as first query but second is not possible.This prove i am wrong . Can u explain it ?

  Read the article

• Why are difference lists more efficient than regular concatenation?

  - by Craig Innes

  I am currently working my way through the Learn you a haskell book online, and have come to a chapter where the author is explaining that some list concatenations can be ineffiecient: For example ((((a ++ b) ++ c) ++ d) ++ e) ++ f Is supposedly inefficient. The solution the author comes up with is to use 'difference lists' defined as newtype DiffList a = DiffList {getDiffList :: [a] -> [a] } instance Monoid (DiffList a) where mempty = DiffList (\xs -> [] ++ xs) (DiffList f) `mappend` (DiffList g) = DiffList (\xs -> f (g xs)) I am struggling to understand why DiffList is more computationally efficient than a simple concatenation in some cases. Could someone explain to me in simple terms why the above example is so inefficient, and in what way the DiffList solves this problem?

  Read the article

• Wordpress Database SQL query help needed

  - by i-CONICA

  Hi, I've written a PHP script to access the latest item from the wordpress database, which it does. But I need to use it twice, once for the latest item from a specific category, and another from a differerent category... But right now I cannot figure out how to put the query together. The post has a post_parent, which in another table, called wp_term_relationships, is referred to as object_id, and has a term_taxonomy_id, which then relates to a different table, called wp_terms where the term_taxonomy_id is now term_id and then you have the category slug name available to select... I really cannot understand how this query would work though. I've made a really crap mock up of it, to try to "visually" explain what i'm trying to do... SELECT * FROM wp_posts WHERE post_status = 'publish' AND (SELECT term_taxonomy_id FROM wp_term_relationships WHERE object_id = post_parent) AND (SELECT slug FROM wp_terms WHERE term_id = term_taxonomy_id) ORDER BY ID DESC LIMIT 1 Really would appreciate some help... Thanks.

  Read the article

• Python grab class in class definition.

  - by epochwolf

  I don't even know how to explain this, so here is the code I'm trying. class Test: type = self.__name__ #self doesn't work, how do I get a reference to Test? class Test2(Test): pass #Test2.type should return "Test2" The reason I'm even trying this is I'm working on creating a base class for an orm I'm using. I want to avoid defining the table name for every model I have. Also knowing what the limits of python is will help me avoid wasting time trying impossible things.

  Read the article

• MS SQL Server 2008 Stored Procedure Result as Column Default Value

  - by user337501

  First of all, thank you guys. You always know how to direct me when I cant even find the words to explain what the heck im trying to do. The default values of the columns on a couple of my tables need to equal the result of some complicated calculations on other columns in other tables. My first thought is to simply have the column default value equal the result of a stored procedure. I would also have one or more of the parameters pulled from the columns in the calling table. I don't know the syntax of how to do it though, and any time the word "stored" and "procedure" land next to each other in google I'm flooded with info on Parameter default values and nothing relating to what I actually want. Half of that was more of a vent than a question...any ideas though? And plz plz dont say "Well, you could use an On-Insert Trigger to..."

  Read the article

• Should I stick only to AWS RDS Automated Backup or DB Snapshots?

  - by James Wise

  I am using AWS RDS for MySQL. With it comes on backup, I understand that amazon provides two types of backup - automated backup and database (DB) snapshot. The difference is explain in here - http://aws.amazon.com/rds/faqs/#23. However, I am still confuse if should I stick to automated backup only or both automated and manual (db snapshots). What do you think guys? What's the setup of your own? I heard to others that automated backup is not reliable due to some unrecoverable database when the DB instance is crashed so the DB snapshots are the way to rescue you. If I will do daily DB snapshots as similar settings to automated backup, I have gonna pay much bunch of bucks. Hope anyone could enlighten me or advise me the right set up. Thanks. James

  Read the article

• Parallel CURL function Help .. php

  - by Webby

  Hello.. Firstly let me explain the code below is just a tiny snippet of the code I'm using on the working site. Basically I'm hoping someone can help me rewrite just the function below to enable parallel CURL calls... that way it will fit nicely into the existing code without me having to rewrite the whole from the ground up like some of the samples I've been finding today any ideas? function get_data($url) { $ch = curl_init(); $timeout = 5; curl_setopt($ch,CURLOPT_URL,$url); curl_setopt($ch,CURLOPT_RETURNTRANSFER,1); curl_setopt($ch,CURLOPT_CONNECTTIMEOUT,5); $data = curl_exec($ch); curl_close($ch); return $data; } p.s. $url goes through a huge bunch of urls in a loop already so I'd hole to keep that intact.. Help always appreciated and rewarded

  Read the article

• How to use JarOutputStream to create a JAR file?

  - by Gili

  How does one create a JAR file programmatically using java.util.jar.JarOutputStream? The JAR file produced by my program looks correct (it extracts fine) but when I try loading a library from it Java complains that it cannot find files which are clearly stored inside it. If I extract the JAR file and use Sun's jar command-line tool to re-compress it the resulting library works fine. In short, something is wrong with my JAR file. Please explain how to create a JAR file programmatically, complete with a manifest file.

  Read the article

• What is this event?

  - by Shawn Mclean

  Could someone explain what this C# code is doing? // launch the camera capture when the user touch the screen this.MouseLeftButtonUp += (s, e) => new CameraCaptureTask().Show(); // this static event is raised when a task completes its job ChooserListener.ChooserCompleted += (s, e) => { //some code here }; I know that CameraCaptureTask is a class and has a public method Show(). What kind of event is this? what is (s, e)?

  Read the article

• question on regular servlets within GWT (working in dev mode ,not working in deployment in tomcat)

  - by molleman

  Hello guys, i am having trouble with my web application developed in GWT. the application allows users to upload and download using an upload servlet and a download servlet, the upload servlet was created using the gwtUpload library. the download servlet is using regular HTTPServlet. when i run the application within eclipse the download servlet works fine, when i deploy it to tomcat, when a user selects to upload a file, the file does not download, when a user selects a link to download a file, this error is returned type Status report message /testhibernategilead/downloadServlet description The requested resource (/testhibernategilead/downloadServlet) is not available. can anyone explain why this is

  Read the article

• C++ - Resources in static library question

  - by HardCoder1986

  Hello! This isn't a duplicate of http://stackoverflow.com/questions/531502/vc-resources-in-a-static-library because it didn't help :) I have a static library with TWO .rc files in it's project. When I build my project using the Debug configuration, I retrieve the following error (MSVS2008): fatal error LNK1241: resource file res_yyy.res already specified Note, that this happens only in Debug and Release library builds without any troubles. The command line for Resources page in project configuration looks the same for every build: /fo"...(Path here)/Debug/project_name.res" /fo"...(Path here)/Release/project_name.res" and I can't understand what's the trouble. Any ideas? UPDATE I don't know why this happens, but when I turn "Use Link-Time Code Generation" option on the problem goes away. Could somebody explain why does this happen? I feel like MS-compiler is doing something really strange here. Thanks.

  Read the article

• How Does Differential Execution Work?

  - by Brian

  I've seen a few mentions of this on SO, but staring at Wikipedia and at an MFC dynamic dialog demo did nothing to enlighten me. Can someone please explain this? Learning a fundamentally different concept sounds nice. Edit: I think I'm getting a better feel for it. I guess I just didn't look at the source code carefully enough the first time. I have mixed feelings about DE at this point. On the one hand, it can make certain tasks considerably easier. On the other hand, getting it up and running (i.e. setting it up in your language of choice) is not easy (I'm sure it would be if I understood it better)...though I guess the toolbox for it need only be made once, then expanded as necessary. I think in order to really understand it, I'll probably need to try implimenting it in another language.

  Read the article

• data between pages: $_SESSION vs. $_GET ?

  - by Haroldo

  Ok, firstly this is not about forms this is about consistent layout as a user explores a site. let me explain: If we imagine a (non-ajax) digital camera online store, say someone was on the DSLR section and specified to view the cameras in Gallery mode and order by price. They then click onto the Compact camera's page. It would be in the users interests if the 'views' they selected we're carried over to this new page. Now, i'd say use a session - am i wrong? are there performance issues i should be aware of for a few small session vars ( ie view=1 , orderby=price) ?

  Read the article

• A resource for installation or setup folder hierarchy of various applications

  - by Luay

  Is there a web site (or something else) that has information on folders and their hierarchy where various programs and applications are installed? Please let me explain. I am writing an application that (part of what it does) references certain files installed by other application. To be able to determine the file paths for these folders I have to download and install each application seperatly on my development pc, search for the file I want, and then write its path in my application. This method is very time consuming and, frankly, boring, as it requires downloading and installing each application (some of them in excess of 600MB) and then locating the required file just to be able to "know" its path. So, I was wondering if there is something that could speed things up. like, for example, a website that would have such information. I tried each of the applications own website for information but no dice. Any help from you will be much appreciated. Many thanks

  Read the article

• How to use DML on Oracle temporary table without generating much undo log

  - by Sambath

  Hi, Using an Oracle temporary table does not generate much redo log as a normal table. However, the undo log is still generated. Thus, how can I write insert, update, or delete statement on a temporary table but Oracle will not generate undo log or generate as little as possible? Moreover, using /+append/ in the insert statement will generate little undo log. Am I correct? If not, could anyone explain me about using the hint /+append/? INSERT /*+APPEND*/ INTO table1(...) VALUES(...); Thank you.

  Read the article

• GQL, Aggregation and Order By

  - by Koran

  Hi, How can GQL support ORDER BY when it does not support aggregation? The question is - if say the result of the query is more than 1000, does ORDER BY return fully ordered list or only the first 1000 items which is then ordered? To explain the question more: is conceptually MIN() same as query.orderby('asc').fetch(1)? If it is properly ordering the list, then how can it not provide COUNT(), since to properly order the list, GQL possibly has to parse through the whole list - in which case, COUNT() is not an issue at all? Or is item indexed and kept in some type of tree so that it does not need to parse it all the time?

  Read the article

• Meaning of the "Unloading class" messages

  - by elec

  Anyone can explain why the lines below appear in the output console at runtime ? (one possible answer would be full permGen, but this can be ruled out since the program only uses 24MB out of the max100MB available in PermGen) [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor28] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor14] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor4] [Unloading class sun.reflect.GeneratedMethodAccessor5] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor38] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor36] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor22] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor8] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor39] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor16] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor2] [Unloading class sun.reflect.GeneratedConstructorAccessor1] The program runs with the following params: -Xmx160M -XX:MaxPermSize=96M -XX:PermSize=96M -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+PrintGCTaskTimeStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -verbose:gc -Xloggc:/logs/gc.log There's plenty of space in the heap and in permGen.

  Read the article

• CInternetSession::OpenURL exception if headers are defined. Works fine if not. Why?

  - by Jesse

  Trying to log the application version details in our weblogs using the headers: Should be a one liner..but for some reason whenever I specify anything but NULL for the headers it causes an exception (InternetOpenUrl() call returns NULL) - anyone able to explain why? CInternetSession internet; CHttpFile * pHttpFile; CString headers;// = APPLICATION_SUITE_NAME; DWORD dwHeadersLength = -1; headers.Format("%s %s %s\n",APPLICATION_SUITE_NAME,SHORT_APPLICATION_VERSION,BUILDNO_STR); pHttpFile =(CHttpFile *) internet.OpenURL(lpszURL, 1, INTERNET_FLAG_TRANSFER_ASCII|INTERNET_FLAG_DONT_CACHE, headers, dwHeadersLength); Without the headers, dwHeadersLength parameter (eg. pass in NULL,-1) then it goes through fine and I see the request come through to our website. But why does it fail if I pass in custom headers?

  Read the article

• What is the Software Development Lifecycle?

  - by j-t-s

  Our investor wants a SDLC. I've never written one before, and I don't have enough time to go and buy a book, or spend much time learning about them. From what I've been told about them, they consist of requirements (what needs to be done), and a list is done. Is this correct? Update: I have found this article which really helps to explain things in simple terms and very quickly. Not that I think an SDLC should be done quickly. In my case, I have no other option.

  Read the article

• Different behaviour of browsers while caching the same file.

  - by Amrita

  I am trying to implement mod_disk_caching. i wrote a php code as shown in the example of the tutorial i was following. i fired the following in the terminal a2enmod cache a2enmod disk_cache /etc/init.d/apache2 force-reload then in the php code "; ? now i tried running it using firefox. In the first execution i got the following timestamp. 1308643975 here, when i press refresh, the timestamp changes (as the file is reloaded from the server) and remains the same when i click the link again (as the file is retrieved from the cache). Now i am trying the same with IExplorer. As per my understanding, the timestamp should be the same as the subsequent request for the file will be retrieved only from the cache. But i got a different timestamp. Can anyone explain me the reason for this? Why is it giving separate timestamps when the browsers are different? Thanks and Regards, AMJ

  Read the article

• Strange client's address returned throug accept(..) function.

  - by Negai

  Hi everyone, I'm a socket programming newbie. Here's a snippet: struct sockaddr_storage client_addr; ... client_addr_size = sizeof(client_addr); client_socket = accept( server_socket, (struct sockaddr *)&client_addr, &client_addr_size ); ... result = inet_ntop( AF_INET, &((struct sockaddr_in *)&client_addr)->sin_addr, client_addr_str, sizeof(client_addr_str) ); Whenever the client connects the address I get is 0.0.0.0 regardless from the host. Can anybody explain, what I'm doing wrong? Thanks.

  Read the article

• why is there extra using where in execution plan of query

  - by user366534

  I see plan of query: EXPLAIN SELECT * FROM `subscribers` WHERE state =4 AND date_added < '2010-12-23 11:47:45' It shows: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE subscribers range state_date_added state_date_added 9 NULL 8 Using where Here is indexes of table: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment subscribers 0 PRIMARY 1 subscriber_id A 382039 NULL NULL BTREE subscribers 0 email_list_id 1 email_address A 191019 NULL NULL BTREE subscribers 0 email_list_id 2 list_id A 382039 NULL NULL BTREE subscribers 1 FK_list_id 1 list_id A 10 NULL NULL BTREE subscribers 1 state_date_added 1 state A 12 NULL NULL BTREE subscribers 1 state_date_added 2 date_added A 8128 NULL NULL BTREE The last two lines describes index what is supposed for the query. Why is there in extra column using where? Even If I fetch only state and date_added column, it has in extra column: Using where; Using index. I understand why it has using index, but I don't understand Using where here.

  Read the article

• Nesting queries in SQL

  - by ZAX

  The goal of my query is to return the country name and its head of state if it's headofstate has a name starting with A, and the capital of the country has greater than 100,000 people utilizing a nested query. Here is my query: SELECT country.name as country, (SELECT country.headofstate from country where country.headofstate like 'A%') from country, city where city.population > 100000; I've tried reversing it, placing it in the where clause etc. I don't get nested queries. I'm just getting errors back, like subquery returns more than one row and such. If someone could help me out with how to order it, and explain why it needs to be a certain way, that'd be great.

  Read the article

< Previous Page | 160 161 162 163 164 165 166 167 168 169 170 171  | Next Page >