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Run a callback only if an attribute has changed in Rails
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Rails 5.1+
class Page < ActiveRecord::Base
before_save :do_something, if: :will_save_change_to_status_id?
private
def do_something
# ...
end
end
The commit that changed ActiveRecord::Dirty is here: https://github.com/rails/rails/commit/16ae3db5a5c6a08383b974ae...
How do we control web page caching, across all browsers?
Our investigations have shown us that not all browsers respect the HTTP cache directives in a uniform manner.
29 Answers
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Can Objective-C switch on NSString?
... @abbood For more information about enum, see the posting NS_ENUM & NS_OPTIONS by Mattt Thompson.
– Basil Bourque
Oct 21 '13 at 21:32
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How do I read configuration settings from Symfony2 config.yml?
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parameters:
contact_email: somebody@gmail.com
You should find the call you are making within your controller now works.
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C++特化模板函数的符号多重定义错误问题 - C/C++ - 清泛网 - 专注C/C++及内核技术
C++特化模板函数的符号多重定义错误问题error LNK2005: "void __stdcall SerializeElements<class CLogEvent> ...fatal error LNK1169: 找到一个或多个多重定义的符号.我...特化模板函数SerializeElements时，报重复定义的错误，如下：
error LNK2005: "void __std...
What are the differences between a multidimensional array and an array of arrays in C#?
...t32 'value') cil managed
{
// Code size 7 (0x7)
.maxstack 8
IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: ldelem.ref
IL_0003: ldarg.2
IL_0004: ldarg.3
IL_0005: stelem.i4
IL_0006: ret
} // end of method Program::SetElementAt
.method private hidebysig static void SetElem...
Generate JSON string from NSDictionary in iOS
...ke easier to read).
@interface NSDictionary (BVJSONString)
-(NSString*) bv_jsonStringWithPrettyPrint:(BOOL) prettyPrint;
@end
.
@implementation NSDictionary (BVJSONString)
-(NSString*) bv_jsonStringWithPrettyPrint:(BOOL) prettyPrint {
NSError *error;
NSData *jsonData = [NSJSONSerial...
How to get the first column of a pandas DataFrame as a Series?
...c wasn't there yet back then. In 2016, the correct answer is Jeff's (after all he's pandas God, mind you ;-)). I'm not sure what's SO's policy regarding update of answers due to API change; I'm honestly surprised by the number of votes for this answer, didn't think it was that useful to people...
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How to Remove ReadOnly Attribute on File Using PowerShell?
...e here? As for Keith's answer, he's using PSCX. Not everyone has those installed and that's not really a case of PowerShell v1 vs. v2.
– Joey
Apr 22 '11 at 9:28
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Why do people put code like “throw 1; ” and “for(;;);” in front of json responses? [du
...ruct, they'll be the attacker's own versions of those objects, with potentially-unexpected behaviour.
For example, you can hack a setter-property into Object, that would betray the values written in object literals:
Object.prototype.__defineSetter__('x', function(x) {
alert('Ha! I steal '+x);
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