How to pass class instance as a handle in Matlab - matlab

Question

A hypothetical scenario to ask my question:
Let's say we have 2 entities: a boss and an employee. When an employee completes a job, he/she wants to let people know. In this case, the boss 'kind of' subscribes to the message and decides what to do
I implemented this interface which has an abstract method that any other class can implemented. In this (cause he/she will decide what he/she wants to do):
classdef (Abstract) Interface < handle
methods
getJobsCompleted(n)
end
end
The boss class inherits Interface and implements the method getJobsCompleted()
classdef Boss < Interface & handle
properties
myEmployee
end
methods
function this = Boss()
this.myEmployee = Employee(this)
this.myEmployee.doJobs();
end
%My boss implements (i.e. decides what to do) the abstract method
function getJobsCompleted(n)
%DO SOMETHING with n
end
end
end
And, finally, the employee performs the jobs and notifies the boss.
classdef Employee < handle
properties
numJobsCompleted;
boss = [];%pointer or reference to Boss instance
end
methods
function this = Employee(myBoss)
this.boss = myBoss; %reference/pointer to my boss so I know who to notify
end
function doJobs()
%% do something then let boss know
this.numJobsCompleted = 40;
this.boss.getJobsCompleted(this.numJobsCompleted);
end
end
end
What I have been attempting to unsuccessfully do is to pass a reference to the Employee class so that he/she knows which boss to notify.
i.e.
in Boss
this.myEmployee = Employee(this)

Answer 1

This will work, you just need to explicitly accept the object instance as an input argument to all methods. You'll need to update the following two function definitions:
function doJobs(this)
function getJobsCompleted(this, n)
That being said, a better way of doing this may be to use events and listeners. You would then have the employee emit a "JobCompleted" event and have the boss listen to those events for all of their employees. This prevents the employee from needing to keep track of their boss.
classdef Boss < handle
properties
Employees
Listeners
end
methods
function this = Boss(employees)
this.Employees = employees;
this.Listeners = addlistener(employees, 'JobCompleted', #this.onJobCompleted);
end
function onJobCompleted(this, employee, evnt)
fprintf('%s completed a job!\n', employee.Name);
end
end
end
Employee.m
classdef Employee < handle
properties
Name
CompletedJobs = 0
end
events
JobCompleted
end
methods
function this = Employee(name)
this.Name = name;
end
function doJob(this)
this.CompletedJobs = this.CompletedJobs + 1;
notify(this, 'JobCompleted')
end
end
end
And use it like:
employees(1) = Employee('Fred');
employees(2) = Employee('Bill');
boss = Boss(employees);
doJob(employees);
doJob(employees(1));