I'm using below class with processQuestion
function to call other methods.
我在下面用processQuestion函数来调用其他方法。
This function is called by calling CONSTANTS
of other classes.
这个函数通过调用其他类的常量来调用。
# Is responsible for executing a particular question. Question types are in the Question object. A question will
# always have a responding method in this class. That method will take the parameters defined by the question and
# should provide the answer in the format expected.
class QuestionProcessor
NO_ROUTE = "NO SUCH ROUTE"
def initialize(routeList)
@routeList = routeList
end
# Finds the method and runs it. This should provide the answer object
def processQuestion(question)
return eval("get"+question.command+"(question)")
end
# Finds the total distance using the exact stations specified, or returns NO_ROUTE if no route was stored in the route list
# this method ignores the constraints and actions
def getDistance(question)
distance = 0
currentStation = nil
question.parameters.each do |nextStation|
if (! currentStation.nil?)
route = @routeList.getDirectRoute(currentStation, nextStation)
if (route.nil?)
return NO_ROUTE
end
distance += route.distance
end
currentStation = nextStation;
end
return distance;
end
# Finds the shortest route possible for the given constraint. This method requires a constraint and action to be provided
def getShortestRoute(question)
startStation = question.parameters[0]
endStation = question.parameters[1]
routeProcessor = ShortestRouteProcessor.new(@routeList, question.constraint, question.action)
routeProcessor.getRoute(startStation, endStation)
return routeProcessor.shortestRoute == Constants::INTEGER_MAX ? NO_ROUTE : routeProcessor.shortestRoute
end
# Counts the number of routes based on the condition provided. Intended to count the number of routes, but could potentially provide a total distance
# or anything else produced by the action.
def getCountRoutes(question)
startStation = question.parameters[0]
endStation = question.parameters[1]
routeProcessor = RouteProcessor.new(@routeList, question.constraint, question.action)
routeProcessor.getRoute(startStation, endStation)
return routeProcessor.totalSuccessfulRoutes
end
end
I thought this is a good approach to remain DRY but I hear eval is evil.
我认为这是保持干燥的好方法,但我听说eval是邪恶的。
Is this good approach or should I look for other ways in a more object oriented way?
这是一种好方法,还是我应该以一种更面向对象的方式寻找其他方法?
2 个解决方案
#1
3
In this case you may safely use send
instead of eval
, like in this example:
在本例中,您可以安全地使用send而不是eval,例如在本例中:
def processQuestion(question)
return send("get#{question.command}", question)
end
Just be aware that send
may be as dangerous as eval
if you do not sanitize your input (question.command
in this case).
只要注意,如果不清理输入(在本例中是question.command),那么send可能与eval一样危险。
If possible, do a white-list filtering before calling send
(or eval
), otherwise someone could pass a command which does something you do not want to do.
如果可能的话,在调用send(或eval)之前进行白名单过滤,否则有人可能会传递一个命令,这个命令执行一些您不希望执行的操作。
#2
3
There is a function in ruby for exactly this reason, the send function. It is part of the Object class so everything has it.
ruby中有一个函数正是因为这个原因,发送函数。它是对象类的一部分,所以所有东西都有它。
read more here: http://ruby-doc.org/core-2.1.1/Object.html#method-i-send
阅读更多:http://ruby-doc.org/core-2.1.1/Object.html method-i-send
for metaprogramming I recommend you read this whole tutorial: https://rubymonk.com/learning/books/2-metaprogramming-ruby/
对于元编程,我建议您阅读本教程:https://rubymonk.com/learning/books/2-metaprogram-ruby/
#1
3
In this case you may safely use send
instead of eval
, like in this example:
在本例中,您可以安全地使用send而不是eval,例如在本例中:
def processQuestion(question)
return send("get#{question.command}", question)
end
Just be aware that send
may be as dangerous as eval
if you do not sanitize your input (question.command
in this case).
只要注意,如果不清理输入(在本例中是question.command),那么send可能与eval一样危险。
If possible, do a white-list filtering before calling send
(or eval
), otherwise someone could pass a command which does something you do not want to do.
如果可能的话,在调用send(或eval)之前进行白名单过滤,否则有人可能会传递一个命令,这个命令执行一些您不希望执行的操作。
#2
3
There is a function in ruby for exactly this reason, the send function. It is part of the Object class so everything has it.
ruby中有一个函数正是因为这个原因,发送函数。它是对象类的一部分,所以所有东西都有它。
read more here: http://ruby-doc.org/core-2.1.1/Object.html#method-i-send
阅读更多:http://ruby-doc.org/core-2.1.1/Object.html method-i-send
for metaprogramming I recommend you read this whole tutorial: https://rubymonk.com/learning/books/2-metaprogramming-ruby/
对于元编程,我建议您阅读本教程:https://rubymonk.com/learning/books/2-metaprogram-ruby/