使用表示变量名称的String来设置变量 [英] Using a String representing the name of a variable to set the variable

问题描述

这是一个我知道可以简化的基本示例，但为了测试，我想以这种方式做到这一点。我想根据附加字符串设置变量（变量cam0和pos1已在类中声明）。附加字符串本质上是一个索引，我将迭代循环将摄像机（cam0，cam1 ..）分配到不同的位置（pos0，pos1 ..）。

This is a basic example that I know can be simplified, but for testing sake, I would like to do this in such a way. I want to set a variable based on an appending string (the variables "cam0" and "pos1" are already declared in the class). The appending string would essentially be an index, and i would iterate through a loop to assign cameras (cam0, cam1..) to different positions (pos0, pos1..).

cam0定义为UIImageView

pos1定义为CGRect

cam0 is defined as an UIImageView
pos1 is defined as a CGRect

这适用于名为coverIndex的NSString变量：

This works for a NSString Variable named coverIndex:

NSString* text = [[NSString alloc] initWithString:@""];
NSLog(@"%@",(NSString *)[self performSelector:NSSelectorFromString([text stringByAppendingString:@"coverIndex"])]);

我为coverIndex设置的正确字符串已记录到控制台。

The correct string that I set for coverIndex was logged to the Console.

现在回到我的UIImageView和CGRect。我想要这个。

Now back to my UIImageView and CGRect. I want this to work.

NSString* camText = [[NSString alloc] initWithString:@"cam"];
NSString* posText = [[NSString alloc] initWithString:@"pos"];

[(UIImageView *)[self performSelector:NSSelectorFromString([camText stringByAppendingString:@"0"])] setFrame:(CGRect)[self performSelector:NSSelectorFromString([posText stringByAppendingString:@"1"])]];

我的错误是请求转换为非标量类型

My error is "Conversion to non-scalar type requested"

这是我发现做这种事情的唯一方法（并让NSLog工作），但我仍然相信有一种更简单的方法。

This is the only way I found to do this sort of thing (and get the NSLog to work), but I still believe there is an easier way.

非常感谢你的帮助：）

推荐答案

使用 KVC ，这是一项令人惊叹的技术，可以满足您的需求：

Use KVC, it's an amazing piece of technology that will do just what you want:

for (int index = 0; index < LIMIT; index++) {

    NSString *posName = [NSString stringWithFormat:@"pos%d", index];
    CGRect pos = [[self valueForKey:posName] CGRectValue];
    NSString *camName = [NSString stringWithFormat:@"cam%d", index];

    UIImageView *cam = [self valueForKey:camName];
    cam.frame = pos;
}

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