Object Literals(提供了很棒的语法糖)

@Object Literals允许你方便地定义数字、数组和字典对象,这个新功能,能让我们少写很多代码.......

//  原先的写法
    NSNumber *oldNumber = [NSNumber numberWithInt:1];
    NSArray  *oldArray= [NSArray arrayWithObjects:@"array1",@"array2",@"array3", nil];
    NSDictionary *oldDictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"dic1",@"key1",@"dic2",@"key2", nil];
    NSString *oldValue = [oldDictionary objectForKey:@"key1"];
    
    //  新写法
    NSNumber *newNumber = @(1);
    NSArray  *newArray = @[@"array1",@"array2",@"array3"];
    NSDictionary *newDictionary = @{@"key1": @"dic1",@"key2":@"dic2"};
    NSString *newValue = newDictionary[@"key1"];
    
    //  整数
    NSNumber *newInt = @(1);
    NSNumber *newUnsigned = @(1U);
    NSNumber *newLong = @(1L);
    
    //  浮点数
    NSNumber *newFloat = @(3.14f);
    NSNumber *newDouble = @(3.14);
    
    //  布尔值
    NSNumber *newYes = @(YES);
    NSNumber *oldNo = @(NO);