Question

I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?.

Here is an example (for simplicity, let’s say there are only two possible algorithms) …

class Foo
{
private:
   // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1);
   AlgorithmInterface* a; 

};

class AlgorithmInterface
{
public:
   virtual void DoSomething() = 0;
};

class Algorithm1 : public AlgorithmInterface
{
public:
   Algorithm1( int i ) : value(i) {}
   virtual void DoSomething(){ // Does something with int value };
   int value;   
};

class Algorithm2 : public AlgorithmInterface
{
public:
   Algorithm2( bool b ) : value(b) {}
   virtual void DoSomething(){ // Do something with bool value };
   bool value;   
};

Answer 1

It would be a valid design because the Strategy pattern asks for an interface to be defined and any class that implements it is a valid candidate to run the strategy code, regardless how it is constructed.