loadobj - Customize load process for objects - MATLAB (original) (raw)

Customize load process for objects

Syntax

Description

Note

The matlab.mixin.CustomElementSerialization class is recommended overloadobj and saveobj because the mixin provides greater control over how objects are serialized and deserialized, including the ability to add, delete, and rename properties. (since R2024b)

[b](#mw%5F6f39094a-b09e-4d5c-b948-26f308176d7b) = loadobj([a](#mw%5F99d96b3c-1005-4a55-9490-68b458061912)) deserializes an object represented by a. Define aloadobj method when objects of a class require special processing when loaded from MAT files. If you define a saveobj method, then define a loadobj method to restore the object to the desired state. If the class of the object defines aloadobj method, load automatically calls it.

example

Examples

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Restore Listener Using loadobj

Listeners cannot be serialized with objects. If your class defines a listener, you can use loadobj to restore it when an instance is deserialized.

Define the BankAccount class. The class includesAccountBalance and AccountStatus properties. The transient property AccountManagerListener holds a listener object that changes AccountStatus based on the value ofAccountBalance.

classdef BankAccount < handle properties (SetObservable,AbortSet) AccountBalance end properties (Transient) AccountManagerListener end properties AccountStatus end methods function obj = BankAccount(initialBalance) obj.AccountBalance = initialBalance; obj.AccountStatus = "New Account"; obj.AccountManagerListener = addlistener(obj,... "AccountBalance","PostSet",@(src,evt)assignStatus(obj)); end function assignStatus(obj,~) if obj.AccountBalance < 0 obj.AccountStatus = "Overdrawn"; else obj.AccountStatus = "Open"; end end end end

Create an instance of BankAccount.

x =

BankAccount with properties:

        AccountBalance: 100
AccountManagerListener: [1×1 event.proplistener]
         AccountStatus: "New Account"

Set the AccountBalance property to a negative amount and check the change to AccountStatus.

x =

BankAccount with properties:

        AccountBalance: -100
AccountManagerListener: [1×1 event.proplistener]
         AccountStatus: "Overdrawn"

If you call save to serialize x,AccountManagerListener is not serialized. To restore the event listener when you call load, define a loadobj method for BankAccount that recreates the listener and assigns it toAccountManagerListener.

methods (Static) function obj = loadobj(obj) if isstruct(obj) initialBalance = obj.AccountBalance; obj = BankAccount(initialBalance); else obj.AccountManagerListener = addlistener(obj,... "AccountBalance","PostSet",@(src,evt)assignStatus(obj)); end end end

Save x and then clear it. Load x to confirmloadobj recreated the event listener.

save("C:_yourpath_\AccountTest.mat","x") clear x load("C:_yourpath_\AccountTest.mat","x") x

x =

BankAccount with properties:

        AccountBalance: -100
AccountManagerListener: [1×1 event.proplistener]
         AccountStatus: "Overdrawn"

Input Arguments

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a — Content to be deserialized

object | structure

Content to be deserialized from the MAT file, which can be:

• An object
• A structure created by load if load cannot resolve the object
• A structure created by the corresponding saveobj method

Output Arguments

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b — Object passed to load function

object

Object passed to the load function by MATLAB®.The value returned by a class loadobj method is typically an object of the class being loaded. However, the loadobj method can return an object of a different class or an updated object that matches a new class definition.

Tips

• Define loadobj as a static method.
• Implement your loadobj method to work with scalar objects or structures. When you deserialize an object array, load callsloadobj on each element of the saved array.
• When a new version of a class removes, renames, or changes the validation for a property, load can generate an error when attempting to set the altered or deleted property. If the class defines a loadobj method, MATLAB returns the saved values to the loadobj method in astruct. If the saved object derives from multiple superclasses that have private properties with same name, thestruct contains only the property value of the most direct superclass.
• When loading a subclass object, load calls only the subclassloadobj method. If a superclass defines a loadobj method, the subclass inherits this method. However, the inherited method might not perform the necessary operations to load the subclass object. Consider overriding superclassloadobj methods if needed for your application. You can also call a superclass loadobj from a subclassloadobj.

Version History

Introduced before R2006a