CODEWITHSUNDEEP
hashmapcrystal-lang
Ujjwal Kumar Gupta
Ujjwal Kumar Gupta

Reputation: 2376

How to store any class object in an hash map

I have a hash map which acts as store of objects - where key is class name & value is object

store = {} of String => Type 

store["Animal"]= Animal.new
store["Book"]= Book.new
store["Car"]= Car.new

Here class is unknown to me, which means i can't use union type. Please tell me how to solve this problem ?

I am trying to create a wrapper around hash map for storage of objects, which will save object & return object by key.

Update 1

Classes will be passed as a parameter - like this 

add_in_store(Animal)
add_in_store(Person)

Update 2

Crystal play link of what i am trying to do - https://play.crystal-lang.org/#/r/8lwx

Solution of problem doesn't have to be in same way as what i m doing. It can be with any other approach like using proc or macro etc.

Upvotes: 0

Views: 429

Answers (1)

Jonne Haß
Jonne Haß

Reputation: 4857

Hash is a generic type, to wrap it in a way where you cannot or don't want to restrict the possible types of the generic arguments, you should make your wrapper itself generic. 

class Store(V)
  @store = {} of String => V 

  def add(name, value : V)
    @store[name] = value 
  end 
end

Then the consumer of your wrapper has to give the possible types.

Upvotes: 1

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