For…in statement Objective-C

问题

I am studying Objective-C and I came across this "for...in" statement. I searched for it but i still don't get how it works. Could someone explain to me in a noob-friendly how this statement works?

回答1:

See fast enumeration documentation.

Basically you'd have, usually, an array, and you can obtain each item in the array with a handy loop instead of using NSEnumerator or an integer count variable. It makes your code much cleaner to ask for each NSString in your array rather than to have to assign to a variable using objectAtIndex for each pass of your loop.

Compare:

for (NSString *string in myArray)
{
    // do stuff...
}

To:

for (int i = 0; i < [myArray count]; i++)
{
    NSString *string = [myArray objectAtIndex:i];
    // Do stuff...
}

来源：https://stackoverflow.com/questions/7476541/for-in-statement-objective-c