//1.快速创建NSNumber对象
        NSNumber *number1 = @20;  //@ + 常量
        int a = 20;
        NSNumber *number2 = @(a);  //@ + (变量)
        //2.快速创建将C语言的字符串常量转为OC的字符串对象
        NSString *str1 = @"Frank";
        //3.快速创建NSArry对象
        NSArray *arr1 = @[@"aa", @"hu", @"ty", @"fd"];
        //4.快速创建NSMutableArry对象
        NSMutableArray *arr2 = [@[@"dg", @"ji", @"gt", @"fg"] mutableCopy];
        //5.快速根据下标取出数组中的元素
        NSString *str2 = arr1[0];
        NSString *str3 = arr2[3];
        //6.快速创建NSDictionary字典对象
        NSDictionary *dic = @{@"name":@"Frank", @"age":@"19", @"gender":@"man"};
        //7.快速创建NSMutableDictionary对象
        NSMutableDictionary *dic1 = [@{@"name":@"Frank", @"age":@"19", @"gender":@"man"} mutableCopy];
        //8.快速的根据key取出对应的value
        NSString *str4 = dic[@"name"];
        NSString *srt5 = dic1[@"age"];

        2.将 NSNumber数据对象转化为基本数据类型
        NSNumber *number1 = @20;
        NSNumber *number2 =@19.9;
        NSNumber *number3 = @NO;
        NSNumber *number4  = @‘m‘;
        int newNumber1 = [number1 intValue];
        NSLog(@"%d", newNumber1);
        float newNumber2 = [number2 floatValue];
        NSLog(@"%.1f", newNumber2);
        BOOL newNumber3 = [number3 boolValue];
        NSLog(@"%d", newNumber3);
        char newNumber4 = [number4 charValue];
        NSLog(@"%c", newNumber4);
        

笑笑语法,语法糖 ---- 字面量