数组Array的基本操作

缺乏、安全感 2023-10-17 02:46 11阅读 0赞

一切都在代码中：

//不可变数组 ；创建之后，不能再改变 ；存放的是对象类型，一定注意不能存放基本类型</s ；
        NSArray  * array = [[NSArray alloc]initWithObjects:@"11",@"222",@"333", nil];
        //获得数组中元素的数目
        NSInteger count = [array count];
       // int count = array.count ;
        NSLog(@"%ld",count);
        
        //根据索引去获得数组中得元素 ；注意 索引从0开始 ，依次加1
        NSString * str =   [array objectAtIndex:2];
        NSLog(@"_______%@",str);
        
        //for循环获得数组中每一个元素：遍历
        for (int i = 0 ; i < array.count; i++)
        {
            NSString * str = [array objectAtIndex:i];
            NSLog(@"str = %@",str);
        }
        
         //reason: '*** -[__NSArrayI objectAtIndex:]: index 5 beyond bounds [0 .. 2]'  数组越界
        //---------------------------------------------
        //可变的数组   可以进行  增、删、改、查四中操作
        NSMutableArray  * mutableArray = [[NSMutableArray alloc]initWithObjects:@"a",@"b",@"c", nil];
        NSInteger mutableCount = mutableArray.count ;
        NSLog(@"mutableCount  = %ld",mutableCount);
        
        //增,最后追加一个元素
        [mutableArray addObject:@"d"];
        //插入 ，在制定的索引位置添加一个元素，之后的元素后移；
        [mutableArray insertObject:@"e" atIndex:2];
        NSLog(@"%@",mutableArray);//a\b\e\c\d
        
    //    [mutableArray removeAllObjects];
    //    [mutableArray removeLastObject];
    //    [mutableArray removeObject:];
        
        //删除制定索引位置的元素
        [mutableArray removeObjectAtIndex:4];
        NSLog(@"%@",mutableArray);//a\b\e\c
        
        //改  用指定的元素替换制定索引位置的元素 ；
        [mutableArray replaceObjectAtIndex:1 withObject:@"f"];
        NSLog(@"%@",mutableArray);//a\f\e\c
        
        //查
        NSString * str00 = [mutableArray objectAtIndex:2];
        NSLog(@"str00 = %@",str00);

数组中存放对象（包括控件），就是一定不能存放基本类型

如，存放imageview对象时

//创建数组，
        NSMutableArray * imageArray = [[NSMutableArray alloc]init];
        //for循环向数组中添加 UIImage类型的对象
        for (int i = 0 ; i < 17; i++)
        {
            //获得图片的名称
            NSString * imageName = [NSString stringWithFormat:@"Fire%d.gif",i+1];
            UIImage * image = [UIImage imageNamed:imageName];
            
            [imageArray addObject:image];
        }

如要存放基本类型，可以转为字符串，或者NSNumber类型，使用时再转回来即可

[array addObject:[NSNumber numberWithBool:YES]];

NSNumber和基本类型的各种转换方法如下：

+ (NSNumber *)numberWithChar:(char)value;
    + (NSNumber *)numberWithUnsignedChar:(unsigned char)value;
    + (NSNumber *)numberWithShort:(short)value;
    + (NSNumber *)numberWithUnsignedShort:(unsigned short)value;
    + (NSNumber *)numberWithInt:(int)value;
    + (NSNumber *)numberWithUnsignedInt:(unsigned int)value;
    + (NSNumber *)numberWithLong:(long)value;
    + (NSNumber *)numberWithUnsignedLong:(unsigned long)value;
    + (NSNumber *)numberWithLongLong:(long long)value;
    + (NSNumber *)numberWithUnsignedLongLong:(unsigned long long)value;
    + (NSNumber *)numberWithFloat:(float)value;
    + (NSNumber *)numberWithDouble:(double)value;
    + (NSNumber *)numberWithBool:(BOOL)value;
    + (NSNumber *)numberWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0);
    + (NSNumber *)numberWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0);