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  • 【Objective-C学习记录】第二天

    1.不可变数组:

      NSArray *array = [[NSArray alloc] initWithObjects:@"1",@"2",@"3",nil];

      判断元素是否存在:

        BOOL res = [array containsObject:@"1"];

      获取最后一个元素:

        NSString *str = [array lastObject];//3

      获取第一个元素:

        NSString *str = [array firstObject];//1

      根据下标获取元素:  

        NSString *str = [array objectAtIndex:2];//3

      根据元素输出下标:

        int index = (int)[array indexOfObject:@"2"];

      数组遍历:

        1.for循环

        2.快速枚举(需要数组元素类型完全一致)

          for(NSString *str in array)

            NSLog(@"%@",str);

    2.可变数组:

      NSMutableArray *array = [[NSMutableArray alloc] init];

      添加元素:

        [array addObject:p];

        [array addObjectsFromArray:array2];

      删除所有元素:

        [array removeAllObjects];

      删除最后一个元素:

        [array removeLastObject];

      删除指定元素:

        [array removeObject:@"2"];

      交换元素位置:

        [array exchangeObjectAtIndex:0 withObjectAtIndex:1];

    字典:

      //内存存储不是连续的

      NSDictionary *dict = [NSDictionary dictionaryWithObject:@"1" forKey:@"a"];

      NSDictionary *dict = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"1",@"2",@"3",nil] forKeys:[NSArray arrayWithObjects:@"a",@"b",@"c",nil]];

      NSDictionary *dict = @{@"1":@"a",@"2":@"b",@"3":@"c"};

      NSString *value = [dict valueForKey:@"a"];//1

      NSString *value2 = [dict objectForKey:@"a"];//1

      NSString *allValues = [dict allValues];//(1,2,3)

      NSString *allKeys = [dict allKeys];//(a,b,c)

      查找值:

        NSArray *array = [dict objectsForKeys:[NSArray arrayWithObjects:@"a",@"b",@"d",nil] notFoundMaker:@"Not Found"];//如果找到值则返回,没找到则返回Not Found

        NSLog(@"%@",array);//(1,2,"Not Found")

      遍历字典:

      1.for in

        for(NSString *key in dict)

          NSLog(@"%@ = %@",key,[dict objectForKey:key]);

      2.枚举器

        NSEnumerator *en = [dict keyEnumerator];

        id key = nil;

        while(key = [en nextObject])

          NSLog(@"Key = %@",key);

      block方法

      [dict enumerateKeysAndObjectsUsingBlock:^(id key,id obj,BOOL *stop){}];

    可变字典:

      NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];

      [dict setObject:@"1" forKey:@"a"];

      [dict setObject:@"2" forKey:@"b"];

      删除所有值对:

        [dict removeAllObjects];

      删除指定值对:

        [dict removeObjectForKey:@"b"];

        [dict removeObjectsForKeys:[NSArray arrayWithObjects:@"a",@"b",nil]];

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  • 原文地址:https://www.cnblogs.com/shvier/p/5017736.html
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