iOS数组常用方法

//数组定义

NSMutableArray* arr = [[NSMutableArray alloc] initWithObjects:@"A",@"B",@"C", nil];

//清空数组:删除数组中的全部元素

[arr removeAllObjects];

//删除数组最后加入的元素

[arr removeLastObject];

//数组拷贝：将一个数组中的全部元素复制到另一个数组中

[arr1 addObjectsFromArray:arr2];

说明：将数组arr2中的全部元素复制到数组arr1中

//从字典组成的数组中：将每个字典中指定key的数据全部取出组成一个数组

    NSMutableArray* arr1 = [[NSMutableArray alloc] init];
    NSMutableDictionary* dic1 = [[NSMutableDictionary alloc]init];
    [dic1 setObject:@"Tom" forKey:@"name"];
    [dic1 setObject:@"male" forKey:@"sex"];
   
    NSMutableDictionary* dic2 = [[NSMutableDictionary alloc]init];
    [dic2 setObject:@"Mike" forKey:@"name"];
    [dic2 setObject:@"female" forKey:@"sex"];
   
    NSMutableDictionary* dic3 = [[NSMutableDictionary alloc]init];
    [dic3 setObject:@"John" forKey:@"name"];
    [dic3 setObject:@"male" forKey:@"sex"];
   
    [arr1 addObject:dic1];
    [arr1 addObject:dic2];
    [arr1 addObject:dic3];
   
    NSLog(@"arr1=%@",arr1);
  //输出：

arr1=(
        {
        name = Tom;
        sex = male;
    },
        {
        name = Mike;
        sex = female;
    },
        {
        name = John;
        sex = male;
    }
)
 
    NSArray* sexArray = [arr1 valueForKey:@"sex"];
    NSLog(@"sexArray=%@",sexArray);
//输出：

sexArray=(
    male,
    female,
    male
)
 
    NSArray* nameArray = [arr1 valueForKey:@"name"];
    NSLog(@"nameArray=%@",nameArray);

//输出：

nameArray=(
    Tom,
    Mike,
    John
)