Class method calls method of other instantiated class

Hello everyone,

I'm new to OOP and have a question.

I have the following class:

classdef Operator 
properties 
        id; 
        offer; 
end 

    methods       
        % Functions 
        function submitOffer(obj) 
            % submit offer 
            centralMarket.enterOffer(obj.offer); 
        end 
    end  

An instance of this class shall pass the variable "offer" to an instance of the class "CentralMarket".

    classdef CentralMarket 
    properties 
        id; 
        orderBook; 
        marketResult; 
    end 

        % Functions 
        function obj = enterOffer(obj, offer) 
            % write offer into the order book 
            w_idx = length(obj.orderBook) + 1; 
            obj.orderBook{w_idx} = offer; 
        end 

For this I call the function "submitOffer" of the initialized class "Operator":

    operator.submitOffer();

But it's not working out the way I want it to. I get the following message:

    Undefined variable "centralMarket" or class "centralMarket.enterOffer".

Of course, I can work around the whole thing as follows:

    centralMarket = centralMarket.enterOffer(operator.offer);

But that wouldn't be pleasant. Is there a way?

Answer 1

[Steven Lord]

If the object stored in the offer property of the Operator class is a CentralMarket object, this should work.

function submitOffer(obj) 
    enterOffer(obj.offer);
end

If it is not a CentralMarket object, but the enterOffer method of the CentralMarket object were a Static method, that could work.

classdef CentralMarket
    % ...
    methods(Static)
        function obj = enterOffer(obj, offer)
            % ...
        end
    end
end

But because enterOffer manipulates properties of the obj object passed into it as input, it's probably not suitable to be a Static method.

You might want to read through the BankAccount and AccountManager classes on this documentation page. You may be able to use them as a model for your application. Alternately, explain in more detail (in words not code) how you want the Operator class method submitOffer and the CentralMarker class to interact with one another and we may be able to help you figure out the best way to implement that interaction.

[Nico Lehmann]

Thank you very much for the quick answer!

As you already said, the objects localMarket and centralMarket must be passed to the instance of the class "Operator" operator. It is important that both objects are handle classes so that no copies are made. Your linked tutorial with the bank account helped a lot here.