Matlab OOP array of objects class

Question

I'd like to understand how Matlab works with array objecs. I've read several posts and the Matlab help for this topic, but I still don't understand it completely.

Let's take a use case: I'd like to manage several measurement channels (the amount of channels can vary). Each measurement channel is an object with several properties. Now I'd like to have a class handling the channels (channelHandler.m). In this class I can simply add a new channel to the array (later on there might be bore functionality).

So what I've tried so far:

1) create the measurementChannel.m class In the constructor I've only set the channel name so far without data.

classdef measurementChannel
%CHANNEL holds an instance of a single channel

properties
    channelData
    channelName = strings
    channelUnit = strings
    channelDataLength    
    channelOriginMeasurementFile
end

methods
    function obj = channelTest(channelName)
        if nargin > 0
            obj.channelName = channelName;
        end
    end
end

end

To test this class I tried this:

channel(1) = measurementChannel('channelA');
channel(2) = measurementChannel('channelB');
channel(1).channelName
channel(2).channelName

which was working well.

2) Now I've created the channelHandler class:

classdef channelHandler

properties (Access = public)
    channelArray
end

methods (Access = public)

    function addChannel(obj, Name)

        testobj = measurementChannel();

        testobj.channelName = Name;

        obj.channelArray = [obj.channelArray testobj];

    end

end

and access this by using the following commands:

createChannels = channelHandler();

createChannels.addChannel('channel1');
createChannels.addChannel('channel2');

createChannels.channelArray(1).channelName
createChannels.channelArray(2).channelName

this fails because channelArray is not defined as an array and will give an error accessing channelArray(2). So I also tried to initialize the array (but then I need to know the amount of channels).

so my questions are: a) do I really need to initialize an array of objects? b) how can I fix the channelHandler class to add objects to the array?

Suever · Accepted Answer · 2016-12-27 14:56:18Z

1

The issue is that you are not inheriting from the handle class and therefore the modifications made within addChannel alter a copy of your object rather than the object itself. If you inherit from handle, the code that you have pasted will work just fine.

classdef channelHandler < handle

answered Dec 27, 2016 at 14:56

Suever

65.6k14 gold badges91 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Christoph Over a year ago

just for my understanding: If I'm using the handle class, only a reference to the object is stored in the channelArray. why is it not possible to store the data itself in the channelArray?

Suever Over a year ago

@Christoph The references are stored in the array, but that's effectively the same as the data itself being stored in the channelArray. All that it means is that if you assign it to a different variable and modify it, that change will be reflected in the original object.

Collectives™ on Stack Overflow

Matlab OOP array of objects class

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related