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Why are #ifndef and #define used in C++ header files?
...he header is included, it checks if a unique value (in this case HEADERFILE_H) is defined. Then if it's not defined, it defines it and continues to the rest of the page.
When the code is included again, the first ifndef fails, resulting in a blank file.
That prevents double declaration of any iden...
Version of SQLite used in Android?
...rt it.
Note: if you want your app to use the same version of SQLite across all Android versions, consider using this 3rd party SQLite support library.
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How do I set up email confirmation with Devise?
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1. Make sure you include confirmable in Model.devise call
class User < ActiveRecord::Base
devise :database_authenticatable, :confirmable ...
end
2. Make sure you add confirmable to the user migration
create_table :users do |t|
t.database_authenticatable
t.confirmabl...
“X-UA-Compatible” content=“IE=9; IE=8; IE=7; IE=EDGE”
...ontent="IE=7; IE=9" />
Renders IE7 and IE8 as IE7, but IE9 as IE9. It allows for different levels of backwards compatibility. In real life, though, you should only chose one of the options:
<meta http-equiv="X-UA-Compatible" content="IE=8" />
This allows for much easier testing and mai...
Javascript - removing undefined fields from an object [duplicate]
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You actually don't even need the ternary operator. Instead you can do (obj[key]===undefined&& delete obj[key]) The reason this works is because and uses short-circuit evaluation, so once the first check fails the second isn'...
How do I delete an Azure storage account containing a leased blob?
...unt can be deleted.
Notes:
This applies even if you've already deleted all of your Virtual Machines and it shows 0; there still will be artifacts under the disks tab.
Disks are detached from a deleted VM asynchronously, it may take a few minutes after the VM is deleted for this field to clear up...
How to read a large file - line by line?
... The for line in f treats the file object f as an iterable, which automatically uses buffered I/O and memory management so you don't have to worry about large files.
There should be one -- and preferably only one -- obvious way to do it.
...
Using ls to list directories and their total sizes
...possible to use ls in Unix to list the total size of a sub-directory and all its contents as opposed to the usual 4K that (I assume) is just the directory file itself?
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What is SQL injection? [duplicate]
...sult of queries, reading data or even changing data that they shouldn't be allowed to do.
Example in PHP:
$password = $_POST['password'];
$id = $_POST['id'];
$sql = "UPDATE Accounts SET PASSWORD = '$password' WHERE account_id = $id";
Now suppose the attacker sets the POST request parameters to "...
Convenient C++ struct initialisation
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Since style A is not allowed in C++ and you don't want style B then how about using style BX:
FooBar fb = { /*.foo=*/ 12, /*.bar=*/ 3.4 }; // :)
At least help at some extent.
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