QF——OC数组

        //NSArray:不可变数组
        
        //NSArray的实例化方法：
        //对象方法：
        NSArray * arr1 = [[NSArray alloc]initWithObjects:@"one",@"two",@"three", nil]; //末尾的nil表示结束符
        NSArray * arr2 = [[NSArray alloc]initWithArray:arr1]; //通过已存在的数组实例化新数组
        
        //类方法：
        NSArray * arr3 = [NSArray arrayWithObjects:@"one",@"two",@"three", nil];
        NSArray * arr4 = [NSArray arrayWithArray:arr3];
        
        //Xcode新版本的便捷方法：
        NSArray * arr5 = @[@"one",@"two",@"three"];  //类似于NSString * str = @"wanger";且此时数组结尾无nil！

        
        //NSArray常用方法：
        NSArray *arr = [NSArray arrayWithObjects:@"one",@"two",@"three",nil];
        
        //求元素个数：count
        NSUInteger count = [arr count];
        NSLog(@"count = %lu",count);
        
        //获取某位置元素
        id obj = [arr objectAtIndex:2];
        NSLog(@"%@",obj);
        //其实这个方法很鸡肋。arr[index]效果一样
        NSLog(@"%@",arr[2]);
        
        //获取某元素的索引
        NSInteger index = [arr indexOfObject:@"one"];
        NSLog(@"index = %lu",index);
        
        //判断该数组是否包含某元素
        BOOL tag = [arr containsObject:@"two"];
        if(tag==YES)
        {
            NSLog(@"嗯，包含了。");
        }else if (tag==NO)
        {
            NSLog(@"没包含。");
        }
        
        //获取数组最后一个元素
        id obj2 = [arr lastObject];
        NSLog(@"lastObject为 %@",obj2);
        
        //将数组各元素连接成字符串对象
        NSString *str = [arr componentsJoinedByString:@"+"];
        NSLog(@"%@",str);

       //将字符串通过分隔符转换成数组
        NSString * str1 = @"welcome to shenzhen";
        NSArray *arr1 = [str1 componentsSeparatedByString:@" "];
        NSLog(@"%lu",[arr1 count]);
        
        NSString *str2 = @"Hi,wang.weclome";
        id seqSet = [NSCharacterSet characterSetWithCharactersInString:@",."];
        NSArray *arr2 = [str2 componentsSeparatedByCharactersInSet:seqSet];
        NSLog(@"%lu",[arr2 count]);
        NSLog(@"%@",arr2);

        NSString *str3 = @"yes i am a bad body";
        NSArray *arr3 = [str3 componentsSeparatedByString:@" "];
        int i;
        NSMutableString *mStr = [NSMutableString stringWithUTF8String:""];
        for (i=(int)[arr3 count]-1; i>=0; i--)
        {
            [mStr appendString:arr3[i]];
            [mStr appendString:@" "];
        }
        NSLog(@"%@",mStr);

        //数组遍历
        NSArray *arr1 = [NSArray arrayWithObjects:@"one",@"two",@"three",nil];
        //1.最基本原始方法：for循环
        
        //2.迭代器
        NSEnumerator *erator = [arr1 objectEnumerator];
        
        id obj;
        while ((obj=[erator nextObject])!=nil)
        {
            NSLog(@"%@",obj);
        }
        
        //3.增强型for循环
        //for(对象类型 对象名 in 列表)
        //优点：不需要开发者判断结束条件，自动结束
        for (id obj in arr1)
        {
            NSLog(@"%@",obj);
        }