Swift，从字符串中获取变量名称

问题描述

我有一个问题。我知道这可以在Ruby中完成，不确定Swift，但从未做过类似的事情。
我正在研究的是一个与此类似的程序：如果用户在TextViewa + b中写入，我的代码应该详细说明变量a和b之间的总和值。
我的意思是，如何从字符串中获取变量名？它有可能吗？

I have a question. I know that this can be done in Ruby, not sure about Swift, but never did anything similar.What I'm working on is a program that works similar to this: if the user writes in a TextView "a + b", my code should elaborate the value of the sum between the variable "a" and "b".What I mean is, how can I get variable names from a string? Is it possible at all?

如果不是，我会使用一个开关（变量名有限），但我需要连接一个变量到用户写的那个。在这个例子中，如果用户写a + b，我的sum函数就像sum（par1，par2），那么，我怎样才能使变量par1指向a和par2指向b？我可以用指针做到这一点吗？还有其他方法吗？

If it's not, I'd use a switch (variable names are limited), but I'd need to "connect" a variable to the one written by the user. In the example, if the user writes "a + b", my sum function is something like "sum(par1,par2)", so, how can I make variable "par1" point to "a" and "par2" point to "b"? I can do that with pointers right? Is there any other way?

我不确定我是否已经清楚，但很难解释

I'm not sure I've been clear, but it's quite hard to explain

推荐答案

检查一下。您可以使用 NSExpression 和 KVC 。

Check this out. You can do with NSExpression and KVC.

class myclass:NSObject {

    var a = 10;
    var b = 20;

    override init() {
        super.init();
    }


}

var obj = myclass();

// Expression from user
var expr:NSString = "a+b" ;

//Operators..
let opSet = NSMutableCharacterSet()
opSet.addCharactersInString("+-*/");


let components:NSArray = expr.componentsSeparatedByCharactersInSet(opSet)
let uniqueChars:NSSet = NSSet(array: components)

for variable in uniqueChars
{
    expr = expr.stringByReplacingOccurrencesOfString ( variable as String,
    withString  : NSString(format: "%d", obj.valueForKey(variable as String) as Int),
    options     : NSStringCompareOptions.LiteralSearch,
    range       : NSMakeRange(0,expr.length)         );

}


var result: AnyObject = NSExpression(format: expr).expressionValueWithObject(nil, context: nil)

print (result);

这篇关于Swift，从字符串中获取变量名称的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！