在Objective-C 2.0中有类似Matlab的eval语句吗？ [英] Is there something like Matlab's eval statement in Objective-C 2.0?

问题描述

我是Objective-C的新手，我正在寻找一个像我在Matlab中使用的 eval 语句。

I am new to Objective-C and I am looking for an eval statement like I have used in Matlab.

如果您对此不熟悉，可以构建一个字符串，然后 eval 该字符串，对待它就像是一行代码。

If you are not familiar with this, you can build a character string and then eval that string, which treats it like it is a line of code.

这是一个例子，你想根据变量foo改变一系列4个按钮之一的背景颜色where = 3，你的按钮名为button1，button2等。

Here is a example where you would want to change the background color of one of a series of 4 buttons based on a variable foo which = 3 and you buttons would be named button1, button2 etc.

NSString* buttonEval = [[NSString alloc] initWithFormat:@"[button%d setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];", foo]

Is有一个声明会评估这个字符串，好像它是一行代码吗？

Is there a statement the will evaluate this string as if it was a line of code?

推荐答案

否;虽然Objective-C是一种动态类型语言，但它仍然是一种编译语言，而不是像Javascript或PHP这样的语言，不是解释语言。

No; although Objective-C is a dynamically typed language, it is still a compiled language, and not an interpreted one, unlike a language such as Javascript or PHP, for example.

对于上面的示例，您可以使用数组存储指向 UIButton 实例的指针：

For the above example, you could use an array to store pointers to your UIButton instances:

buttonArray = [[NSMutableArray alloc] init];
...
UIButton *aButton; //Reference to a UIButton instance
[buttonArray addObject:aButton];

稍后检索指向 UIButton 的指针你要调用方法。

And later retrieve a pointer to the UIButton that you want to call the method on.

[[buttonArray objectAtIndex:foo] setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];

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