Objective-C 学习笔记 - part 8 - 快速枚举

快速枚举使用的语法：

for ( Type newVariable in expression ) { statements }

or

Type existingItem;

for ( existingItem in expression ) { statements }

枚举期间对象不能被改变。

使用快速枚举的三个类：

NSArray, NSDictionary, NSSet

如何使用：

NSArray *array = [NSArray arrayWithObjects:

@"One", @"Two", @"Three", @"Four", nil];

for (NSString *element in array) {

NSLog(@"element: %@", element);

}

NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:

@"quattuor", @"four", @"quinque", @"five", @"sex", @"six", nil];

NSString *key;

for (key in dictionary) {

NSLog(@"English: %@, Latin: %@", key, [dictionary objectForKey:key]);

}

也可以使用 enumeration :

NSArray *array = [NSArray arrayWithObjects:

@"One", @"Two", @"Three", @"Four", nil];

NSEnumerator *enumerator = [array reverseObjectEnumerator];

for (NSString *element in enumerator) {

if ([element isEqualToString:@"Three"]) {

break;

}

}

NSString *next = [enumerator nextObject];

// next = "Two"