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  • Rails :dependent => :destroy VS :dependent => :delete_all

    - by Sergey
    In rails guides it's described like this: "Objects will be in addition destroyed if they’re associated with :dependent = :destroy, and deleted if they’re associated with :dependent = :delete_all." Right, cool. But what's the difference between being destroyed and being deleted? I tried both and it seems to do the same thing.

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  • Best way to test for a variable's existence in PHP; isset() is clearly broken

    - by chazomaticus
    From the isset() docs: isset() will return FALSE if testing a variable that has been set to NULL. Basically, isset() doesn't check for whether the variable is set at all, but whether it's set to anything but NULL. Given that, what's the best way to actually check for the existence of a variable? I tried something like: if(isset($v) || @is_null($v)) (the @ is necessary to avoid the warning when $v is not set) but is_null() has a similar problem to isset(): it returns TRUE on unset variables! It also appears that: @($v === NULL) works exactly like @is_null($v), so that's out, too. How are we supposed to reliably check for the existence of a variable in PHP? Edit: there is clearly a difference in PHP between variables that are not set, and variables that are set to NULL: <?php $a = array('b' => NULL); var_dump($a); PHP shows that $a['b'] exists, and has a NULL value. If you add: var_dump(isset($a['b'])); var_dump(isset($a['c'])); you can see the ambiguity I'm talking about with the isset() function. Here's the output of all three of these var_dump()s: array(1) { ["b"]=> NULL } bool(false) bool(false) Further edit: two things. One, a use case. An array being turned into the data of an SQL UPDATE statement, where the array's keys are the table's columns, and the array's values are the values to be applied to each column. Any of the table's columns can hold a NULL value, signified by passing a NULL value in the array. You need a way to differentiate between an array key not existing, and an array's value being set to NULL; that's the difference between not updating the column's value and updating the column's value to NULL. Second, Zoredache's answer, array_key_exists() works correctly, for my above use case and for any global variables: <?php $a = NULL; var_dump(array_key_exists('a', $GLOBALS)); var_dump(array_key_exists('b', $GLOBALS)); outputs: bool(true) bool(false) Since that properly handles just about everywhere I can see there being any ambiguity between variables that don't exist and variables that are set to NULL, I'm calling array_key_exists() the official easiest way in PHP to truly check for the existence of a variable. (Only other case I can think of is for class properties, for which there's property_exists(), which, according to its docs, works similarly to array_key_exists() in that it properly distinguishes between not being set and being set to NULL.)

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  • diff between tables

    - by www.yegorov-p.ru
    I have two tables, with the same structure, for example: table "first' with columns 'a','b','c' and table 'second' with the same columns. How to find difference betweet those two tables? Of course, I can make some script on python, that will make set(a)-set(b), but I think there is some way to do it in mysql.

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  • Git aliases that are stored in origin

    - by jga
    I use git with a big development team and I'd like to have a set of aliases be common across every developer. They change every so often, so I'd like to store them in origin somehow. Is there any way to set that up in git? I'm using gitosis for the git server (not sure if that would make a difference).

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  • WPF or Windows Forms

    - by Luminose
    I've been playing around with C# console applications for about a year and I want to move on to creating GUI applications. I have never done any GUI development besides basic Java applications, but I want to continue using C#. Should I start learning Windows Forms or jump straight to WPF? Is there a huge difference? Does WPF build on top of Windows Forms or are they totally different?

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  • c# object instantiation

    - by user1112111
    What's the difference between: Object o = new Object(); o.foo(); and new Object().foo(); (assuming I do not need the reference afterwards) ? Are there any reasons for using one instead of the other one (e.g. memory usage) ?

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  • How to run Red5 applications on a remote server?

    - by domi
    I've got a really nasty problem... I wrote a Red5 app and so on and it is running perfectly on my local computer. Now the problem occurs = How can I make this program work on a remote server? Local : Mac OS X 10.5 - Red5 0.63 Server: CentOS 5 - Red5 0.90 Maybe it's because of the version difference. But I can't test Red5 0.90 locally because it won't start up and I can't install the 0.63 version on the server because of missing dependencies (and broken links to them...)

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  • Licensing WPF application

    - by Macros
    Does anyone have any guidance on the best way to manage licensing for a WPF application? I would like to have different levels of licensing (Free, Trial and Professional). The app itself will probably be distributed with a WiX installer (if that makes any difference)

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  • Can I use declare-const to eliminate the forall universal quantifier?

    - by monica
    I have some confusion of using universal quantifier and declare-const without using forall (set-option :mbqi true) (declare-fun f (Int Int) Int) (declare-const a Int) (declare-const b Int) (assert (forall ((x Int)) (>= (f x x) (+ x a)))) I can write like this: (declare-const x Int) (assert (>= (f x x) (+ x a)))) with Z3 will explore all the possible values of type Int in this two cases. So what's the difference? Can I really use the declare-const to eliminate the forall quantifier?

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  • how to convert all characters to their html entity equivalent using PHP

    - by Ashley Ward
    I want to convert this [email protected] to &#104;&#101;&#108;&#108;&#111;&#064;&#100;&#111;&#109;&#097;&#105;&#110;&#046;&#099;&#111;&#109; I have tried: url_encode($string) this provides the same string I entered, returned with the @ symbol converted to %40 also tried: htmlentities($string) this provides the same string right back. I am using a UTF8 charset. not sure if this makes a difference....

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  • Variable declarations in header files - static or not?

    - by Rob
    When refactoring away some #defines I came across declarations similar to the following in a C++ header file: static const unsigned int VAL = 42; const unsigned int ANOTHER_VAL = 37; The question is, what difference, if any, will the static make? Note that multiple inclusion of the headers isn't possible due to the classic #ifndef HEADER #define HEADER #endif trick (if that matters). Does the static mean only one copy of VAL is created, in case the header is included by more than one source file?

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  • == Operator and operands

    - by rahul
    I want to check whether a value is equal to 1. Is there any difference in the following lines of code Evaluated value == 1 1 == evaluated value in terms of the compiler execution

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  • Can't access font resource in Silverlight class library

    - by Matt
    I have a reasonably large Silveright 3.0 project on the go, and I'm having issues accessing a couple of custom font resources from within one of the assemblies. I've got a working test solution where I have added a custom font as a resource, and can access it fine from XAML using: <TextBlock Text="Test" FontFamily="FontName.ttf#Font Name" /> The test solution consists of the TestProject.Application and the TestProject.Application.Web projects, with all the fun and games obviously in the TestProject.Application project However, when I try this in my main solution, the fonts refuse to show in the correct type face (instead showing in the default font). There's no difference in the way the font has been added to project between the test solution and the main solution, and the XAML is identical. However, there is a solution layout difference. In the main solution, as well as having a MainApp.Application and MainApp.Application.Web project, I also have a MainApp.Application.ViewModel project and a MainApp.Application.Views project, and the problem piece of XAML is the in the MainApp.Application.Views project (not the .Application project like the test solution). I've tried putting the font into either the .Application or .Application.Views project, tried changing the Build Action to Content, Embedded Resource etc, all to no avail. So, is there an issue accessing font resources from a child assembly that I don't know about, or has anyone successfully done this? My long term need will be to have the valid custom fonts being stored as resources in a separate .Application.FontLibrary assembly that will be on-demand downloaded and cached, and the XAML controls in the .Application.Views project will need to reference this FontLibrary assembly to get the valid fonts. I've also tried xcreating this separate font library assembly, and I can't seem to get the fonts from the second assembly. As some additional information, I've also tried the following font referencing approaches: <TextBlock Text="Test" FontFamily="/FontName.ttf#Font Name" /> <TextBlock Text="Test" FontFamily="pack:application,,,/FontName.ttf#Font Name" /> <TextBlock Text="Test" FontFamily="pack:application,,,/MainApp.Application.Views;/FontName.ttf#Font Name" /> <TextBlock Text="Test" FontFamily="pack:application,,,/MainApp.Application.Views;component/FontName.ttf#Font Name" /> And a few similar variants with different assembly references/sub directories/random semi colons. And so far nothing works... anyone struck this (and preferably solved it)?

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  • Specifying schema for temporary tables

    - by Tom Hunter
    I'm used to seeing temporary tables created with just the hash/number symbol, like this: CREATE TABLE #Test ( [Id] INT ) However, I've recently come across stored procedure code that specifies the schema name when creating temporary tables, for example: CREATE TABLE [dbo].[#Test] ( [Id] INT ) Is there any reason why you would want to do this? If you're only specifying the user's default schema, does it make any difference? Does this refer to the [dbo] schema in the local database or the tempdb database?

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  • What is the relationship between domNode and htmlelement?

    - by Turtle
    Hello, I am confused about the two terms. What is the difference in browser-side javascript programming? I use dojo as framework. And there is only the concept of domNode. But browser debugger always told me something as htmlelement. Are they just the same thing with different names, or with some subtle differences? Thanks.

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  • Get number of concurrent users online - ASP.NET

    - by Srikanth
    I would like to know the number of users logged into my ASP.NET 2.0 application. Points to be considered: 1) Simplest way would be to use Application or Cache object to have the counts on Session start or end. However this would fail if there is a worker process recycle. Wouldn't it? 2) Should't make a difference whether the session is inproc/state server managed/ or SQL server managed. 3) Should preferably be seamless to a web-farm architecture.

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  • post increment vs pre increment [closed]

    - by mousey
    Possible Duplicate: Difference between i++ and ++i in a loop? Hi, Can some one please help me when to use pre increment or post increment in a for loop. I am getting the same results for both the loops! I also would like to know when and where to choose one between the two. Thanks in advance.

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  • LINQ entity query performance

    - by Abdel Olakara
    Hi all, I have a silly question. I would like to know if there is performance deference in these two quries: var cObject = from cust in entities.Customer where cust.id == cid select cust; and var cObject = entities.Customer.First( c=> c.id == cid); My query return only one record as I am querying with the primary key. But do they make any difference?

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