遍历NSArray, NSDictionary, NSSet的方法总结

1，for循环读取

NSArray:
NSArray *array = /*…*/
for(int i=0; i<array.count; i++)
{
     id object = array[i];
     // do sth
}

NSDictionary:
NSDictionary *dic = /*…*/
NSArray *keys = [dic allKeys];
for(int i=0; i<keys.count; i++)
{
     id key = keys[i];
     id value = dic[key];
     //do sth
}

NSSet:
NSSet *set = /*…*/
NSArray *objects = [set allObjects];
for(int i=0; i<objects.count; i++)
{
     id object = objects[i];
     //do sth
}

2, NSEnumerator类来循环

NSArray:
NSArray *array = /*…*/
NSEnumerator *enumerator = [array objectEnumerator];
id object;
while((object = [enumerator nextObject]) != nil)
{
    //do sth with 'object'
}

NSDictionary:
NSDictionary *dic = /*…*/
NSEnumerator *enumerator = [dic keyEnumerator];
id key;
while((key = [enumerator nextObject]) != nil)
{
    id value = dic[key];
    //do sth
}

NSSet:
NSSet *set = /*…*/
NSEnumerator *enumerator = [set objectEnumerator];
id object;
while((object = [enumerator nextObject]) != nil)
{
    //do sth with 'object'
}

//逆序
NSArray:
NSArray *array = /*…*/
NSEnumerator *enumerator = [array reverseObjectEnumerator];
id object;
while((object = [enumerator nextObject]) != nil)
{
    //do sth with 'object'
}

3, 快速遍历

NSArray:
NSArray *array = /*…*/
for(id object in array){
    //do sth with 'object'
}

NSDictionary:
NSDictionary *dic = /*…*/
for(id key in dic){
    id value = dic[key];
    //do sth with 'value'
}

NSSet:
NSSet *set = /*…*/
for(id object in set){
    //do sth with 'object'
}

//逆序
NSArray:
NSArray *array = /*…*/
for(id object in [array reverseObjectEnumerator]){
    //do sth with 'object'
}

4， 块枚举法

NSArray:        -(void) enumerateObjectsUsingBlock:(void(^)(id object, NSUInteger idx, BOOL *stop)) block;
NSDictionary:    -(void) enumerateKeysAndObjectsUsingBlock(void(^)(id key, id object, BOOL *stop)) block;
NSSet:            -(void) enumerateObjectsUsingBlock:(void(^)(id object, BOOL *stop)) block;

逆序或者并发遍历，使用带有‘选项掩码’的块遍历方法：
NSArray:        -(void) enumerateObjectsWithOptions:(NSEnumerationOptions)options
                                         usingBlock:(void(^)(id object, NSUInteger idx, BOOL *stop)) block;
NSDictionary:    -(void) enumerateKeysAndObjectsWithOptions:(NSEnumerationOptions)options
                                                usingBlock:(void(^)(id key, id object, BOOL *stop)) block;
NSSet:            -(void) enumerateObjectsWithOptions:(NSEnumerationOptions)options
                                         usingBlock:(void(^)(id object, BOOL *stop)) block;

其中：NSEnumerationOptions类型是个Enum，其各种取值可用“按位或”（bitwise OR）连接，用以表明遍历方式。
NSEnumerationConcurrent:并发方式执行各轮迭代
NSEnumerationReverse:逆向

NSArray:
NSArray *array = /*…*/
[array enumerateObjectsUsingBlock:
    ^(id object, NSUInteger idx, BOOL *stop){
        //do sth with 'object'
        if(shouldstop){
            *stop = YES;
        }
    }]

NSDictionary:
NSDictionary *dic = /*…*/
[dic enumerateKeysAndObjectsUsingBlock:
    ^(id key, id object, BOOL *stop){
        //do sth
        if(shouldstop){
            *stop = YES;
        }
    }]

NSSet:
NSSet *set = /*…*/
[set enumerateObjectsUsingBlock:
    ^(id object, BOOL* stop){
        //do sth
        if(shouldstop){
            *stop = YES;
        }
    }]

//逆序、并发
NSArray:
NSArray *array = /*…*/
[array enumerateObjectsWithOptions:NSEnumerationReverse|NSEnumerationConcurrent
                        usingBlock:^(id object, NSUInteger idx, BOOL* stop){
                            //do sth
                            if(shouldstop){
                                *stop = YES;
                            }
                        }]