Easily testing if a string is nil or empty

admin — Tue, 26 Feb 2013 13:16:57 +0000

A very common idiom:


if ([string length]) {

// It's a string of at least one char, and is not null.

}

Works because calling a method on nil is not an error – just silently returns nil, which is also false.

Proper thread-safe singleton

admin — Tue, 26 Feb 2013 12:26:31 +0000

The following is a correct thread-safe implementation of the singleton +sharedInstance method, which relies on GCD:


+ (id)sharedInstance;
{
 static id sharedInstance = nil;
 static dispatch_once_t once = 0;
 dispatch_once(&once,
 ^{ sharedInstance = [[self alloc] init]; }
 );
 return sharedInstance;
}

A2 Apps » Idioms

Easily testing if a string is nil or empty

Proper thread-safe singleton