[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];