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Run a callback only if an attribute has changed in Rails
...
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...
Why do you need explicitly have the “self” argument in a Python method?
...hing is implied or assumed, parts of the implementation are exposed. self.__class__, self.__dict__ and other "internal" structures are available in an obvious way.
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In C#, should I use string.Empty or String.Empty or “” to intitialize a string?
...1
.locals init ([0] string test1,
[1] string test11)
IL_0000: nop
IL_0001: ldsfld string [mscorlib]System.String::Empty
IL_0006: stloc.0
IL_0007: ldloc.0
IL_0008: stloc.1
IL_0009: ret
} // end of method Form1::Test1
.method private hidebysig instance void ...
Can I have onScrollListener for a ScrollView?
...dited Sep 16 '16 at 6:48
Pavneet_Singh
33.3k55 gold badges3939 silver badges5757 bronze badges
answered Apr 29 '14 at 13:06
...
Dynamic variable names in Bash
...ay, with command names as keys.
# Requires bash 4, though
declare -A magic_variable=()
function grep_search() {
magic_variable[$1]=$( ls | tail -1 )
echo ${magic_variable[$1]}
}
If you can't use associative arrays (e.g., you must support bash 3), you can use declare to create dynamic var...
Unzip a file with php
...pen('file.zip');
if ($res === TRUE) {
$zip->extractTo('/myzips/extract_path/');
$zip->close();
echo 'woot!';
} else {
echo 'doh!';
}
Also, as others have commented, $HTTP_GET_VARS has been deprecated since version 4.1 ... which was a reeeeeally long time ago. Don't use it. Use the $_...
How can I extract the folder path from file path in Python?
....path.split(os.path.abspath(existGDBPath))
('T:\\Data\\DBDesign', 'DBDesign_93_v141b.mdb')
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Batch File; List files in directory, only filenames?
...answered May 3 '18 at 10:14
Mike_GreMike_Gre
8111 silver badge33 bronze badges
...
What really happens in a try { return x; } finally { x = null; } statement?
...ged
{
.maxstack 1
.locals init (
[0] int32 CS$1$0000)
L_0000: call int32 Program::SomeNumber()
L_0005: stloc.0
L_0006: leave.s L_000e
L_0008: call void Program::Foo()
L_000d: endfinally
L_000e: ldloc.0
L_000f: ret
.try L_0000 to L_0008 finally hand...
What are 'get' and 'set' in Swift?
...y can set the members value to anything less than 2:
class family {
var _members:Int = 2
var members:Int {
get {
return _members
}
set (newVal) {
if newVal >= 2 {
_members = newVal
} else {
println('error: cannot have family with less than 2 members')
...