将String转换为运算符-Swift

Question

I have many variations of String equations in my program.

" 1 + 9 X 8"

" 4 + 6"

" 5 / 9 + 7"

" 3 X 8"

So, what I want to do is to perform the calculation and give the result. However, I am not able to figure out a way to read the operator characters ("+ / X +") and fit it to the equation. Hope my question is clear.

Note: I am able to read the digit characters, which is simple a String to Int conversion. But, I am having difficulties converting the String equivalent of the characters (" X / + -") to its operators. How can I do this ?

If this is not possible, can someone suggest a workaround.

Answer 1

try something like this

var s = " 1 + 9 X 8"
s = s.replacingOccurrences(of: "X", with: "*")
let expn = NSExpression(format:s)
print("\(expn.expressionValue(with: nil, context: nil) ?? 0)")