OC_NSArray

// OC的數組
// OC裏的數組存放的是對像

    NSArray *arr = [[NSArray alloc] init];

// count:數組的元素個數

    NSLog(@"%ld", arr1.count);

// OC數組也通過下標取值

    NSLog(@"%@", [arr1 objectAtIndex:0]);
    NSLog(@"%@", arr1[0]);

// 判斷是否有指定字符串

    NSLog(@"%d", [arr1 containsObject:@"2"]);

// 向數組內添加對象

    Student *stu1 = [[Student alloc] initWithName:@"張三"];
    Student *stu2 = [[Student alloc] initWithName:@"李四"];
    Student *stu3 = [[Student alloc] initWithName:@"王二麻子"];
    NSArray *arr = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];
    NSArray *arr = [NSArray arrayWithObjects:stu1, stu2, stu3, nil];

// 快速枚舉:能快速遍歷數組等容器對象
// 都是對容器裏對象的遍歷
// 爲了增加代碼可讀性,避免不必要的錯誤, 儘量讓forin的前部分類型和數組內元素的類型相同

    for (NSString *str in arr) {
        NSLog(@"%@", str);
    }

// 遍歷學生姓名

    Student *stu1 = [[Student alloc] initWithName:@"張三"];
    Student *stu2 = [[Student alloc] initWithName:@"李四"];
    Student *stu3 = [[Student alloc] initWithName:@"王二麻子"];
    NSArray *arr = @[stu1, stu2, stu3];
    for (Student *stu in arr) {
            NSLog(@"%@", stu.name);
    }

---

// 可變數組

    NSMutableArray *arr = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3", @"4" ,nil];
    // 添加一個字符串
    [arr addObject:@"5"];
    NSLog(@"%@", arr);

    // 移除下標2的字符
    [arr removeObjectAtIndex:2];
    NSLog(@"%@", arr);

    // 插入一個字符串
    [arr insertObject:@"6" atIndex:3];
    NSLog(@"%@", arr);

    // 替換一個字符串
    [arr replaceObjectAtIndex:3 withObject:@"7"];
    NSLog(@"%@", arr);

    // 交換兩個字符串
    [arr exchangeObjectAtIndex:3 withObjectAtIndex:4];
    NSLog(@"%@", arr);

    // 清除數組
    [arr removeAllObjects];
    NSLog(@"%@", arr);