iOS中使用@方法快速创建对象

       

                在iOS中有大量的@打头的快捷写法，总结如下

NSString

@"My String"     //得到一个__NSCFConstantString类型的对象

NSNumber
@32     @3.22346432  @YES  @'V'  @3.2F   //__NSCFNumber

NSArray

@[@"1",@"2",[NSNull null]]  //__NSArrayI最后的null也算一个元素

NSDictionary *dictionary= @{                                                           @"first":@[@"1",@"2",@"3",[NSNull null]],                               

                           @"second":@3.14,

                           @"third":@"hello world"                                                                    };

//__NSDictionaryI