data access object pattern in matlab

%% DataAccessObject.m

classdef (Abstract) DataAccessObject < handle
    % DataAccessObject is an abstract class that defines the interface for
    % accessing data in a database.
    
    methods (Abstract)
        % Abstract methods to be implemented by subclasses.
        data = read(obj, id)
        update(obj, id, data)
        delete(obj, id)
        create(obj, data)
    end
    
end

%% ConcreteDataAccessObject.m

classdef ConcreteDataAccessObject < DataAccessObject
    % ConcreteDataAccessObject is a concrete implementation of the DataAccessObject.
    % For the sake of simplicity, it uses an in-memory data store.
    
    properties
        data
    end
    
    methods
        function obj = ConcreteDataAccessObject()
            % Initialize an empty data store.
            obj.data = struct('id', {}, 'value', {});
        end
        
        function data = read(obj, id)
            % Lookup an item in the data store by ID.
            item = obj.findItem(id);
            if isempty(item)
                data = [];
                return
            end
            data = item.value;
        end
        
        function update(obj, id, data)
            % Update an existing item in the data store by ID.
            item = obj.findItem(id);
            if isempty(item)
                error('Item not found: %d', id);
            end
            item.value = data;
        end
        
        function delete(obj, id)
            % Delete an item from the data store by ID.
            item = obj.findItem(id);
            if isempty(item)
                error('Item not found: %d', id);
            end
            obj.data(item.index) = [];
        end
        
        function create(obj, data)
            % Create a new item in the data store.
            id = obj.generateId();
            obj.data(end+1) = struct('id', id, 'value', data);
        end
    end
    
    methods (Access = private)
        function item = findItem(obj, id)
            % Lookup an item in the data store by ID.
            item = [];
            for i = 1:numel(obj.data)
                if obj.data(i).id == id
                    item = struct('index', i, 'value', obj.data(i).value);
                    break
                end
            end
        end
        
        function id = generateId(obj)
            % Generate a new unique ID for a new item.
            if isempty(obj.data)
                id = 1;
            else
                id = obj.data(end).id + 1;
            end
        end
    end
    
end
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dao = ConcreteDataAccessObject();

% Create a new item.
data = 42;
dao.create(data);

% Read the item back by ID.
id = 1;
readData = dao.read(id);

% Update the item.
newData = 43;
dao.update(id, newData);

% Delete the item.
dao.delete(id);
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