Using containers.Map as a Class's property

I am having a problem in Matlab while using container.Map as a property of a class. I have a class Sensor with one property which is an object of containers.Map. The problem is, I cannot modify this property for one Sensor object without modifying map in other Sensor object. This property looks to be shared among objects of class Sensor. See below for explanation.

classdef Sensor
    properties 
        id
        map=containers.Map;
    end
end

s1=Sensor;
s2=Sensor;

s1.map('key1')='value1';

s2.map

At this point s2.map also has same content as s1.map.

Has anyone faced this before or any particular solution. I just changed from table to containers.Map because of the flexibility and speed.

Thanks Saurav

Answer 1

[Steven Lord]

From the documentation for how to initialize property values:

"There are two basic approaches to initializing property values:

• In the property definition — MATLAB evaluates the expression only once and assigns the same value to the property of every instance.
• In a class constructor — MATLAB evaluates the assignment expression for each instance, which ensures that each instance has a unique value."

You're initializing the property to a containers.Map in the property definition, and additionally a containers.Map has handle semantics. Initialize it instead in the constructor.

[Saurav]

Thanks very much, I didn't have a clue about it.