[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

 #pragma mark create a array
 void arrayCreate()
 {
     //Create an empty array
     NSArray *array = [NSArray array];

     //Create an array with one element
     array = [NSArray arrayWithObject:@""];

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

     NSUInteger count =[array count];
     NSLog(@"%@", count);

     [array release];
 }

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"];

 #pragma mark common use
 void arrayUser()
 {
     NSArray *array = [NSArray arrayWithObjects:@"a", @"b", @"c", nil];
     if ([array containsObject:@"a"])
     {
         NSLog(@"Contans a");
     }

     NSString *last = [array lastObject];
     NSLog(@"%@", last);

     NSString *str = [array objectAtIndex:];
     NSLog(@"%@", str);

     NSUInteger location = [array indexOfObject:@"c"];
     NSLog(@"%@", location);

     [array release];
 }

 #pragma memory manage
 void memoryManage()
 {
     Student *stu1 = [[Student alloc] init];
     Student *stu2 = [[Student alloc] init];
     Student *stu3 = [[Student alloc] init];

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

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

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

     [stu1 release];
     [stu2 release];
     [stu3 release];

     [array release];

 }

 

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

 void arrayMessage()
 {
     Student *stu1 = [[Student alloc] init];
     Student *stu2 = [[Student alloc] init];
     Student *stu3 = [[Student alloc] init];

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

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

     [stu1 release];
     [stu2 release];
     [stu3 release];

     [array release];
 } 

 

2.遍历

(1)for 循坏

 void arrayLoop()
 {
     Student *stu = [[Student alloc]init];
     NSArray *array = [[NSArray alloc] initWithObjects:stu, @"", @"", nil];
     unsigned long count = array.count;
 //    for (int i=0; i<count; i++)
 //    {
 //        id obj = [array objectAtIndex:i];
 //        NSLog(@"%i - %@", i, obj);
 //    }

     int i = ;
     for (id obj in array)
     {
         NSLog(@"%i - %@", i, obj);
         i++;
     }

     [stu release];
     [array release];
 }

 

（2）使用Block进行循环处理

 void arrayLoopByBlock()
 {
     Student *stu = [[Student alloc]init];
     NSArray *array = [[NSArray alloc] initWithObjects:stu, @"", @"", nil];

     [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
         NSLog(@"%zi - %@", idx, obj);
         if (idx == )
         {
             *stop = YES;
         }
     }];

     [stu release];
     [array release];
 }

 

(3).迭代器

 void arrayLoopByEnumerator()
 {
     Student *stu = [[Student alloc]init];
     NSArray *array = [[NSArray alloc] initWithObjects:stu, @"", @"", nil];

 //    NSEnumerator *e = [array objectEnumerator];
     NSEnumerator *e = [array reverseObjectEnumerator];
     id obj = nil;
     while (obj = [e nextObject])
     {
         NSLog(@"The element is %@", obj);
     }

     [stu release];
     [array release];
 }

创建整数数组

(1)

      NSArray *array61 = [NSArray arrayWithObjects:@, @, @, @, @, @, @, @, @, @, nil];

实际上是把数字自动转化成了NSNumber类型

 

 

(2)不能用于NSMutableArray

 NSArray *array61 = @[@, @, @, @, @, @, @, @, @, @];