iOS之《Effective Objective-C 2.0》读书笔记（48）

第48条：多用块枚举，少用for循环

1.基本的for循环

NSArray *array = /*...*/;
for (int i = 0; i < anArray.count; i++)
{
id object = anArray[i];
//Do something with 'object'
}

2.NSEnumerator遍历法

NSArray *anArray = /* ... */;
NSEnumerator *enumerator = [anArray objectEnumerator];
id object;
while ((object = [enumerator nextObject]) != nil)
{
// Do something with 'object'
}

NSArray *anArray = /* ... */;
NSEnumerator *enumerator = [anArray reverseObjectEnumerator];
id object;
while ((object = [enumerator nextObject]) != nil)
{
// Do something with 'object'
}

3.快速遍历

NSArray *anArray = /* ... */;
for (id object in anArray)
{
// Do something with 'object'
}

4.块枚举法

//1>NSArray
NSArray *anArray = /* ... */;
[anArray enumerateObjectsUsingBlock:^(id object, NSUInteger idx, BOOL *stop)
{
// Do something with 'object'
if (shouldStop)
{
*stop = YES;
}
}];

//2>Dictionary
NSDictionary *aDictionary = /* ... */;
[aDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id object, BOOL *stop)
{
// Do something with 'key' and 'object'
if (shouldStop)
{
*stop = YES;
}
}];
//3>Set
NSSet *aSet = /* ... */;
[aSet enumerateObjectsUsingBlock:^(id object, BOOL *stop)
{
// Do something with 'object'
if (shouldStop)
{
*stop = YES;
}
}];

- (void)enumerateObjectsWithOptions:(NSEnumerationOptions)options
usingBlock:(void(^)(id obj, NSUInteger idx, BOOL *stop))block;

- (void)enumerateKeysAndObjectsWithOptions:(NSEnumerationOptions)options
usingBlock: (void(^)(id key, id obj, BOOL *stop))