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JavaScript hashmap equivalent
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Hash your objects yourself manually, and use the resulting strings as keys for a regular JavaScript dictionary. After all, you are in the best position to know what makes your objects unique. That's what I do.
Example:
var key = function(obj){
// Some un...
Does Python have “private” variables in classes?
...ass variables. In Java, nothing prevents you from doing the same if you really want to - after all, you can always edit the source of the class itself to achieve the same effect. Python drops that pretence of security and encourages programmers to be responsible. In practice, this works very nicely...
When to encode space to plus (+) or %20?
...value is query value with a space, but the folder name in the path is literally foo+bar, not foo bar.
%20 is a valid way to encode a space in either of these contexts. So if you need to URL-encode a string for inclusion in part of a URL, it is always safe to replace spaces with %20 and pluses with ...
find: missing argument to -exec
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A -exec command must be terminated with a ; (so you usually need to type \; or ';' to avoid interpretion by the shell) or a +. The difference is that with ;, the command is called once per file, with +, it is called just as few times as possible (usually once, but there is a maxi...
What's the difference between URI.escape and CGI.escape?
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There were some small differences, but the important point is that URI.escape has been deprecated in Ruby 1.9.2... so use CGI::escape or ERB::Util.url_encode.
There is a long discussion on ruby-core for those interested which also mentions WE...
Run a single migration file
... ruby file:
rails console
>> require "db/migrate/20090408054532_add_foos.rb"
>> AddFoos.up
Note: newer versions of rails may require AddFoos.new.up rather than AddFoos.up.
An alternative way (without IRB) which relies on the fact that require returns an array of class names:
script/...
What is the difference between shallow copy, deepcopy and normal assignment operation?
...ble towards the existing object. The docs explain the difference between shallow and deep copies:
The difference between shallow and deep copying is only relevant for
compound objects (objects that contain other objects, like lists or
class instances):
A shallow copy constructs a new...
How to keep environment variables when using sudo
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To allow -E (preserve environment) for wget, you need to specify the SETENV tag on the sudo rule that allows the running of wget -- Example: <username> ALL=(root) NOPASSWD:SETENV: <path to wget>
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Is it better in C++ to pass by value or pass by constant reference?
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It used to be generally recommended best practice1 to use pass by const ref for all types, except for builtin types (char, int, double, etc.), for iterators and for function objects (lambdas, classes deriving from std::*_function).
This was es...
How do you rename a MongoDB database?
... changes to every shard if the DB is sharded, plus the config servers have all the shard metadata in terms of namespaces with their full names.
There would be absolutely no way to do this on a live system.
To do it offline, it would require re-writing every single database file to accommod...