Objective-C学习篇09—NSNumber与笑笑语法
NSNumber
由于数组,字典,集这三个容器中只能存放对象类型的数据,如果想把基本数据类型的数据存放到这三个容器中,需要把基本数据类型转化为对象类型,此时就要借助于NSNumber 这个类.
NSNumber 继承自NSValue, 数字类,主要的作用是将基本数据类型转换为NSNumber对象类型,也能将对象类型转换为基本数据类型
整型
int a = 100; 创建NSnumber对象 numberWithInt: NSNumber *intNumber = [NSNumber numberWithInt:a]; 即实现了将基本数据类型转化为对象类型 NSLog(@"intNumber = %@", intNumber); 反之,将对象类型转换为基本数据类型 .intValue int b = intNumber.intValue; // 属性,相当于 [intNumber intvalue]; NSLog(@"b = %d", b);
2015-12-04 13:06:17.252 OCNSNumber[1659:136457] intNumber = 100
2015-12-04 13:06:17.253 OCNSNumber[1659:136457] b = 100
浮点型
float c = 3.14;
NSNumber *floatNumber = [NSNumber numberWithFloat:c]; numberWithFloat:
NSLog(@"floatNumber = %@", floatNumber);
float d = floatNumber.floatValue; floatValue
NSLog(@"d = %.2f", d);
字符型
char e = 'a';
字符类型的转化为数字对象 numberWithChar:
NSNumber *charNumber = [NSNumber numberWithChar:e];
NSLog(@"charNumber = %@", charNumber);
char f = charNumber.charValue; .charValue
NSLog(@"f = %c", f);
短整型
short g = 10;
NSNumber *shortNumber = [NSNumber numberWithLong:g]; numberWithLong:
NSLog(@"shortNumber = %@", shortNumber);
short h = shortNumber.shortValue; .shortValue
NSLog(@"h = %d", h);
小练习
// int n1 = 10, n2 = 22, n3 = 18, n4 = 15;
要求:将上面四个变量放到数组对象中,然后排序
// 转化为对象类型
NSNumber *m1 = [NSNumber numberWithInt:n1];
NSNumber *m2 = [NSNumber numberWithInt:n2];
NSNumber *m3 = [NSNumber numberWithInt:n3];
NSNumber *m4 = [NSNumber numberWithInt:n4];
// 装进数组对象中
NSArray *array = [NSArray arrayWithObjects:m1, m2, m3, m4, nil];
// 对数组对象中的元素进行排序
NSArray *sortArray = [array sortedArrayUsingSelector:@selector(compare:)];
NSLog(@"%@", sortArray);
2015-12-04 13:15:23.908 OCNSNumber[1667:140688] (
10,
15,
18,
22
)
总结: 基本数据类型转化为对象: 使用 [NSNumber numberWith+基本数据类型的类型名];反之,将对象类型转化为基本数据类型: 基本数据类型+Value;
笑笑语法
下面是关于一些笑笑语法的使用
笑笑语法,也就是字面量,是一种简洁表示数据的方式
1.对象数据类型的数据表示可以直接使用 @
比如: 拿100 来讲,一般的做法是:
NSNumber *number = [NSNumber numberWithInt:100];
NSLog(@"%@", number);
使用笑笑语法可以这样打印对象
NSLog(@"%@", @100);
2. 不可变数组的笑笑语法 使用 @[ ] 中括号中放对象
NSArray *nameArray2 = @[@"zhangSan", @"liSi", @"wangEr"];
NSLog(@"%@", nameArray2);
3. 可变数组笑笑语法 @[].mutableCopy;
NSMutableArray *mArray2 = @[@"1", @"2", @"3"].mutableCopy; // 可变的都加 .mutableCopy
NSLog(@"%@", mArray2);
4. 使用笑笑语法直接通过数组名加下标进行赋值
mArray2[0] = @100;
NSLog(@"%@", mArray2);
/*
2015-12-04 13:27:55.632 OCNSNumber[1690:146656] (
100,
2,
3
)
*/
5. 字典的笑笑语法
通常
NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:@"xiaoZe", @"1", @"kunLing", @"2", @"sunLi", @"3", nil];
NSLog(@"%@", dic);
笑笑语法 @{ 键:值,... };
NSDictionary *dic2 = @{@"1":@"xiaoZe", @"2":@"kunLing", @"3":@"sunLi"};
NSLog(@"%@", dic2);
6. 可变字典(只有可变才能修改) @{键:值,...}.mutableCopy
NSMutableDictionary *mDic = @{@"1":@"a", @"2":@"b", @"3":@"c"}.mutableCopy;
NSLog(@"%@", mDic);
[mDic setObject:@"A" forKey:@"1"];
NSLog(@"%@", mDic);
7. 修改key值对应的value值
mDic[@"2"] = @"L";
NSLog(@"%@", mDic);
NSString *value = [mDic objectForKey:@"2"];
NSLog(@"%@", value);
8.取出key值对应的value
NSLog(@"%@", mDic[@"3"]);
本节打印结果:
2015-12-04 13:31:10.137 OCNSNumber[1700:148140] intNumber = 100
2015-12-04 13:31:10.138 OCNSNumber[1700:148140] b = 100
2015-12-04 13:31:10.138 OCNSNumber[1700:148140] floatNumber = 3.14
2015-12-04 13:31:10.138 OCNSNumber[1700:148140] d = 3.14
2015-12-04 13:31:10.139 OCNSNumber[1700:148140] charNumber = 97
2015-12-04 13:31:10.139 OCNSNumber[1700:148140] f = a
2015-12-04 13:31:10.139 OCNSNumber[1700:148140] shortNumber = 10
2015-12-04 13:31:10.139 OCNSNumber[1700:148140] h = 10
2015-12-04 13:31:10.139 OCNSNumber[1700:148140] (
10,
15,
18,
22
)
2015-12-04 13:31:10.139 OCNSNumber[1700:148140] 100
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] 100
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] (
zhangSan,
liSi,
wangEr
)
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] (
1,
2,
3
)
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] (
100,
2,
3
)
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] {
1 = xiaoZe;
2 = kunLing;
3 = sunLi;
}
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] {
1 = xiaoZe;
2 = kunLing;
3 = sunLi;
}
2015-12-04 13:31:10.140 OCNSNumber[1700:148140] {
1 = a;
2 = b;
3 = c;
}
2015-12-04 13:31:10.141 OCNSNumber[1700:148140] {
1 = A;
2 = b;
3 = c;
}
2015-12-04 13:31:10.155 OCNSNumber[1700:148140] {
1 = A;
2 = L;
3 = c;
}
2015-12-04 13:31:10.155 OCNSNumber[1700:148140] L
2015-12-04 13:31:10.155 OCNSNumber[1700:148140] c