Call Superclass Constructor ExplicitlyExplicitly calling each superclass constructor from a subclass constructor enables you to: Show
If you do not explicitly call the superclass constructors from the subclass constructor, MATLAB implicitly calls these constructors with no arguments. The superclass constructors must support the no argument syntax to support implicit calls, and the constructors are called in the order they appear at the top of the class block, from left to right. To change the order in which MATLAB calls the constructors or to call constructors with arguments, call the superclass constructors explicitly from the subclass constructor. If you do not define a subclass constructor, you can call the default constructor with superclass arguments. For more information, see Default Constructor and Implicit Call to Inherited Constructor. Call Superclass Constructor from SubclassTo call the constructor for each superclass within the subclass constructor, use the following syntax:
Where For
example, the following segment of a class definition shows that a class called classdef Stocks < Assets methods function s = Stocks(asset_args,...) if nargin == 0 % Assign values to asset_args end % Call asset constructor s@Assets(asset_args); ... end end end Subclass Constructors provides more information on creating subclass constructor methods. Reference Superclasses Contained in PackagesIf a superclass is contained in
a package, include the package name. For example, the classdef Stocks < finance.Assets methods function s = Stocks(asset_args,...) if nargin == 0 ... end % Call asset constructor (asset_args); ... end end end Initialize Objects Using Multiple SuperclassesTo derive a class from multiple superclasses, initialize the subclass object with calls to each superclass constructor: classdef Stocks < finance.Assets & Taxable methods function s = Stocks(asset_args,tax_args,...) if nargin == 0 ... end % Call asset and member class constructors (asset_args) s@Taxable(tax_args) ... end end end Subclass Constructor ImplementationTo ensure that your class constructor supports the zero arguments syntax, assign default values to input argument variables before calling the superclass constructor. You cannot conditionalize a subclass call to the superclass constructor. Locate calls to superclass constructors outside any conditional code blocks. For example, the classdef Stocks < finance.Assets properties NumShares Symbol end methods function s = Stocks(description,numshares,symbol) if nargin == 0 description = ''; numshares = 0; symbol = ''; end (description); s.NumShares = numshares; s.Symbol = symbol; end end end Call Only Direct Superclass from ConstructorCall only direct superclass constructors from a subclass constructor. For example, suppose class The following implementations of
classes Class classdef A properties x y end methods function obj = A(x) ... obj.x = x; end end end Class classdef B < A methods function obj = B(x,y) ... obj@A(x); obj.y = y; end end end Class classdef C < B methods function obj = C(x,y) ... obj@B(x,y); end end end Related Topics
What happens if superclass does not have default constructor?This default constructor will call the no-argument constructor of the superclass. In this situation, the compiler will complain if the superclass doesn't have a no-argument constructor so you must verify that it does.
What happens if a subclass does not have a constructor?If the subclass has no constructor at all, the compiler will automatically create a public constructor that simply calls through to the default constructor of the superclass.
What will happen if we dont call super () from subclass?If we call "super()" without any superclass
Actually, nothing will be displayed. Since the class named Object is the superclass of all classes in Java. If you call "super()" without any superclass, Internally, the default constructor of the Object class will be invoked (which displays nothing).
Why you would need to call the superclass constructor from its subclass?It is required if the parameterized constructor (a constructor that takes arguments) of the superclass has to be called from the subclass constructor. The parameterized super() must always be the first statement in the body of the constructor of the subclass, otherwise, we get a compilation error.
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