从字符串中解析方法并将其存储在数据库中

Question

I want to allow users to specify a function for calculating some property and want to store this function in a generic class. That is, each instance of the class have the same interface, but the result of calling the 'calculate' method varies depending on the user supplied function

I would also like to serialize this class and store it in a database for later use. This is what I am thinking

class LogicalCharge < Charge
    attr_reader :name, :type, :formula, :threshold

    def initialize(name: nil, type: nil, formula: nil, threshold: nil)
      super(name: name, type: type)
      @formula = formula
      @threshold = threshold
    end

    def parse(formula: nil)

    end

    def calculate(dimensions: nil)
      parse(formula: formula).call(dimensions) < threshold
    end

Any advice on how best to proceed from here?

Answer 1

I would suggest a different approach where you have a hierarchy of related classes, one for each of your current variations of the calculate function, and a table with fields for the class name and each of the parameters for running it.

As the classes will all conform to the same interface, this should work well. You can then sanitize the user input cleanly and avoid the horrible security implications of letting users put executable code directly on your server.