OC基础_数组

来源：互联网发布：淘宝4px递四方速递运费编辑：程序博客网时间：2024/04/28 12:54

OC里的数组存放的都是对象

*********************不可变数组******************************

1.创建不可变的空数组

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

NSArray *arr = @[@"1", @"2", @"3", @"4", @"5”];

2.count:数组元素的个数

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

3.通过下标取值,返回一个对象

NSLog(@"%@",[arr objectAtIndex:1] );//方法1

NSLog(@"%@", arr[1]);//方法2

4.for循环对数组遍历

for (NSInteger i = 0; i < arr.count; i++) {

NSLog(@"%@", arr[i]);

}

5.判断6在不在数组里

NSLog(@"%d", [arr containsObject:@"6"]);

6.为Student类创建4个对象

Student *stu1 = [[Student alloc]initWithName:@"商帅"];

Student *stu2 = [[Student alloc]initWithName:@"腾飞"];

Student *stu3 = [[Student alloc]initWithName:@"刘珊珊"];

Student *stu4 = [[Student alloc]initWithName:@"杨林"];

//放到一个数组里(创建不可变数组并赋值)

NSArray *arr = [[NSArray alloc]initWithObjects:stu1,stu2,stu3,stu4 ,nil]; //方法1:自定义初始化

NSArray *arr = [NSArray arrayWithObjects:stu1, stu2, stu3, stu4,nil]; //便利构造器

NSArray *arr = @[stu1, stu2, stu3, stu4];//方法3:字面量

//遍历该数组

快速枚举:能快速遍历数组等容器对象都是对容器里的每一元素的遍历

为了增加代码的阅读性,避免不必要的错误,尽量让forin的前面部分的类型和数组里元素类型相同

for (Student *stu in arr) {

NSLog(@"%@", stu.name);

}

7.数组的嵌套遍历

//将4个对象分别装在两个数组,然后再合并到一个数组,最后遍历学生姓名

NSArray *arr1 = @[stu1, stu2, stu3];

NSArray *arr2 = @[stu4];

NSArray *arr = @[arr1, arr2];

for (NSArray *temp in arr) {

for (Student *stu in temp) {

NSLog(@"%@", stu.name);

}

例:

NSArray *arr1 = @[@"雪男", @"萌萌", @"叶婷",@"腾飞”];

NSArray *arr2 = @[@"星期一", @"水电费", @"火车",@"哈哈"];

NSArray *arr = @[arr1, arr2];

//对arr进行遍历

for (NSArray *temp in arr) {

for (NSString *str in temp) {

NSLog(@"%@", str);

}

*****************************可变数组*****************************

1.创建可变空数组

NSMutableArray *arr = [[NSMutableArray alloc]init]; //自定义初始化

NSMutableArray *arr1 = [NSMutableArray array]; //便利构造器

2.不可变数组变可变数组

NSArray *arr = @[@"1", @"2"];

NSMutableArray *muArr = [NSMutableArray arrayWithArray:arr];

3.字符串操作

NSMutableArray *arr = [[NSMutableArray alloc]initWithObjects:@"1", @"2", @"3", @"4", nil];

(1)添加一个字符串

[arr addObject:@"234”]; //添加到数组的最后一位

NSLog(@"%@", arr);

(2)移除下标2的字符串

[arr removeObjectAtIndex:2];

NSLog(@"%@", arr);

(3)插入一个字符串

[arr insertObject:@"66" atIndex:1];

NSLog(@"%@", arr);

(4)替换一个字符串

[arr replaceObjectAtIndex:3 withObject:@"10"];

(5)交换两个字符串

[arr exchangeObjectAtIndex:2 withObjectAtIndex:3];

NSLog(@"%@", arr);

(6)清空数组

[arr removeAllObjects];

例题: for (Book *temp in bookArr) {

if ([temp.bookName isEqualToString:@"三国演义"]) {

temp.bookPrice = 200;

}

0 0