NSMutableArray （可变数组）继承NSArry（不可变数组）

1.创建对象的方式

1.1初始化方式

    NSMutableArray *array = [[NSMutableArray alloc]initWithCapacity:10];

1.2遍历构造器

    NSMutableArray *array1 =[NSMutableArray arrayWithCapacity:10];

1.3字面量

    NSMutableArray *array2 =[@[@"aa",@"bb"]mutableCopy];

2.添加元素

2.1直接添加元素

   [array addObject:@"zhangsan"];
    NSLog(@"array = %@",array);// array = zhangsan

   [array addObject:@"wangwu"];
    NSLog(@"array = %@",array);
    /*array = (
     zhangsan,
     wangwu
     )
     */

2.2指定位置交通添加

     //在下标是1的地方添加zhaoliu
    [array insertObject:@"zhaoliu" atIndex:1];
    NSLog(@"array = %@",array);
    /*数组是从0开始算起
     array = (
     zhangsan,
     zhaoliu,
     wangwu
     )
     */
   
   //在下标是3的地方添加zhangsan
   [array insertObject:@"zhangsan" atIndex:3];
    NSLog(@"array = %@",array);
    /*(
     zhangsan,
     zhaoliu,
     wangwu,
     zhangsan
     )*/

3.删除

3.1移除所有zhangsan的元素

    [array removeObject:@"zhangsan"];
    NSLog(@"array = %@",array);
    /*(
     zhaoliu,
     wangwu
     )*/

3.2移除下标是1的元素

    [array removeObjectAtIndex:1];
    NSLog(@"array = %@",array);
    /*(
     zhaoliu
     )*/

3.3移除最后一个元素

    [array removeLastObject];

3.4//移除所有元素（删除后数组为空）

    [array removeAllObjects];

给数组添加元素

    [array addObject:@"zhangsan"];
    [array addObject:@"lisi"];
    [array addObject:@"wangwu"];
    [array addObject:@"zhangsan"];
    NSLog(@"array = %@",array);
    /*array = (
     zhangsan,
     lisi,
     wangwu,
     zhangsan
     )*/

3.4移除某一个范围

    [array removeObjectsInRange:NSMakeRange(1,3)];
    NSLog(@"array = %@",array);
    /*array = (
     zhangsan
     )*/
    //移除某一个范围后面的元素
    //[array removeObject:@"zhangsan"inRange:NSMakeRange(1, 3)];

给数组添加元素

    [array addObject:@"lisi"];
    [array addObject:@"wangwu"];
    [array addObject:@"zhaoliu"];
    NSLog(@"array = %@",array);
    /*array = (
     zhangsan,
     lisi,
     wangwu,
     zhaoliu
     )*/

4.交换指定位置上的两个元素

    [array exchangeObjectAtIndex:0 withObjectAtIndex:2];
    NSLog(@"array1 = %@",array);
    /* (
     wangwu,
     lisi,
     zhangsan,
     zhaoliu
     )*/

5.替换数组中的一个元素

    [array replaceObjectAtIndex:3 withObject:@"xueren"];
    NSLog(@"array2 = %@",array);
    /* (
     wangwu,
     lisi,
     zhangsan,
     xueren
     )*/

For循环里面不允许去更改数组的长度,但是移除最后一个元素不影响数组的运行

    //如果删除lisi 数组的长度就会改变从而崩溃
    for (NSString *str in array) {
        if ([str isEqualToString:@"xueren"]) {
            [array removeObject:@"xueren"];
        
        }
    }
    NSLog(@"%@",array);
        /*(
     lisi,
     zhaoliu
     )*/