[OC Foundation框架 - 7] NSArray的创建与遍历

NSArray是不可变的，不能先创建再添加元素

NSArray可以放入任何OC对象，但不能放入基本数据类型、结构体、枚举等非OC对象

不能存储nil

 

A.常用方法1

1. 创建
2. 返回用量
3. 是否含有某元素
4. 最后的元素
5. 取得某位置的元素

当一个对象放入数组的时候，这个对象的计数器加1

 1 #pragma mark create a array

 2 void arrayCreate()

 3 {

 4     //Create an empty array

 5     NSArray *array = [NSArray array];

 6    

 7     //Create an array with one element

 8     array = [NSArray arrayWithObject:@"123"];

 9    

10     array = [NSArray arrayWithObjects:@"a", @"b", @"d", nil];

11    

12     NSUInteger count =[array count];

13     NSLog(@"%@", count);

14    

15     [array release];

16 }

最后的nil用作标示数组的结束，不会被存储进数组元素，不允许在其他地方插入

error:    array = [NSArray arrayWithObjects:@"a”, nil, @"d"];

 1 #pragma mark common use

 2 void arrayUser()

 3 {

 4     NSArray *array = [NSArray arrayWithObjects:@"a", @"b", @"c", nil];

 5     if ([array containsObject:@"a"])

 6     {

 7         NSLog(@"Contans a");

 8     }

 9    

10     NSString *last = [array lastObject];

11     NSLog(@"%@", last);

12    

13     NSString *str = [array objectAtIndex:1];

14     NSLog(@"%@", str);

15    

16     NSUInteger location = [array indexOfObject:@"c"];

17     NSLog(@"%@", location);

18    

19     [array release];

20 }

21 

22 #pragma memory manage

23 void memoryManage()

24 {

25     Student *stu1 = [[Student alloc] init];

26     Student *stu2 = [[Student alloc] init];

27     Student *stu3 = [[Student alloc] init];

28    

29     NSLog(@"stu1: %zi", [stu1 retainCount]);

30    

31     NSArray *array = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];

32    

33     NSLog(@"stu1: %zi", [stu1 retainCount]);

34    

35     [stu1 release];

36     [stu2 release];

37     [stu3 release];

38    

39     [array release];

40    

41 }

 

B.常用方法2

 

1.给数组所有元素发送消息，调用同一个方法

 1 void arrayMessage()

 2 {

 3     Student *stu1 = [[Student alloc] init];

 4     Student *stu2 = [[Student alloc] init];

 5     Student *stu3 = [[Student alloc] init];

 6    

 7     NSArray *array = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];

 8    

 9     [array makeObjectsPerformSelector:@selector(test2:) withObject:@"test2"];

10    

11     [stu1 release];

12     [stu2 release];

13     [stu3 release];

14    

15     [array release];

16 } 

 

2.遍历

(1)for 循坏

 1 void arrayLoop()

 2 {

 3     Student *stu = [[Student alloc]init];

 4     NSArray *array = [[NSArray alloc] initWithObjects:stu, @"2", @"3", nil];

 5     unsigned long count = array.count;

 6 //    for (int i=0; i<count; i++)

 7 //    {

 8 //        id obj = [array objectAtIndex:i];

 9 //        NSLog(@"%i - %@", i, obj);

10 //    }

11    

12     int i = 0;

13     for (id obj in array)

14     {

15         NSLog(@"%i - %@", i, obj);

16         i++;

17     }

18    

19     [stu release];

20     [array release];

21 }

 

（2）使用Block进行循环处理

 1 void arrayLoopByBlock()

 2 {

 3     Student *stu = [[Student alloc]init];

 4     NSArray *array = [[NSArray alloc] initWithObjects:stu, @"2", @"3", nil];

 5    

 6    

 7     [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

 8         NSLog(@"%zi - %@", idx, obj);

 9         if (idx == 1)

10         {

11             *stop = YES;

12         }

13     }];

14    

15     [stu release];

16     [array release];

17 }

 

(3).迭代器

 1 void arrayLoopByEnumerator()

 2 {

 3     Student *stu = [[Student alloc]init];

 4     NSArray *array = [[NSArray alloc] initWithObjects:stu, @"2", @"3", nil];

 5    

 6 //    NSEnumerator *e = [array objectEnumerator];

 7     NSEnumerator *e = [array reverseObjectEnumerator];

 8     id obj = nil;

 9     while (obj = [e nextObject])

10     {

11         NSLog(@"The element is %@", obj);

12     }

13    

14     [stu release];

15     [array release];

16 }

创建整数数组

(1)
    

1      NSArray *array61 = [NSArray arrayWithObjects:@0, @1, @2, @3, @4, @5, @6, @7, @8, @9, nil];

实际上是把数字自动转化成了NSNumber类型

 

 

(2)不能用于NSMutableArray

        

1 NSArray *array61 = @[@0, @1, @2, @3, @4, @5, @6, @7, @8, @9];