OC语法简写

NSNumber

[NSNumber numberWithInt:666]                等价于 @666  
[NSNumber numberWithLongLong:666ll]         等价于 @666ll
[NSNumber numberWithUnsignedLong:666ul]     等价于 @666ul    
[NSNumber numberWithFloat:66.6f]            等价于 @66.6f  
[NSNumber numberWithDouble:66.6]            等价于 @66.6  
[NSNumber numberWithBool:YES]               等价于 @YES 
[NSNumber numberWithChar:‘A’]               等价于 @‘A’

NSArray

[NSArray array]                             等价于 @[]  
[NSArray arrayWithObject:a]                 等价于 @[a] 
[NSArray arrayWithObjects:a, b, c, nil]     等价于 @[a,b,c]

[arr objectAtIndex:i]                       等价于 arr[i];  
[arr replaceObjectAtIndex:i withObject:newObj] 
                                            等价于 arr[i] = newObj

NSMutableArray * mutableArr = [@[a,b,c] mutableCopy];

NSDictionary

[NSDictionary dictionary]                   等价于 @{}  
[NSDictionary dictionaryWithObject:obj1 forKey:key1]   
                                            等价于 @{key1:obj1}  
[NSDictionary dictionaryWithObjectsAndKeys:obj1, key1, obj2, key2, obj3, key3, nil] 
                                            等价于 @{key1:obj1,key2:obj2,key3:obj3}

[dic objectForKey:key]                      等价于 dic[key]  
[dic setObject:obj forKey:key]              等价于 dic[key] = obj

NSMutableDictionary * mutableDic = [@{key1:obj1} mutableCopy];