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Constructor Declaration
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Declaration: Definitions vs Declarations, Definitions and Declarations (computer programming): Type declaration - User-defined type declaration, Variable declaration - Constant declaration, Class declaration - Object declaration, Constructor declaration - Destructor declaration, Struct declaration - Record declaration, Function declaration - Method declaration, Lambda declaration - Anonymous function declaration, Enumerator declaration, Pointer declaration, Generic declaration - Template declaration, Interface declaration - Protocol declaration - Trait declaration, Namespace declaration, Package declaration, Module declaration, Alias declaration, Import declaration - Export declaration, Macro declaration. Programming terms. (navbar_declaration)
- Snippet from Wikipedia: Constructor (object-oriented programming)
In class-based, object-oriented programming, a constructor (abbreviation: ctor) is a special type of function called to create an object. It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables.
A constructor resembles an instance method, but it differs from a method in that it has no explicit return type, it is not implicitly inherited and it usually has different rules for scope modifiers. Constructors often have the same name as the declaring class. They have the task of initializing the object's data members and of establishing the invariant of the class, failing if the invariant is invalid. A properly written constructor leaves the resulting object in a valid state. Immutable objects must be initialized in a constructor.
Most languages allow overloading the constructor in that there can be more than one constructor for a class, with differing parameters. Some languages take consideration of some special types of constructors. Constructors, which concretely use a single class to create objects and return a new instance of the class, are abstracted by factories, which also create objects but can do so in various ways, using multiple classes or different allocation schemes such as an object pool.
Language Specifics
1. Bash Scripting
2. C Language
3. C++
4. C#
5. Clojure
6. COBOL
- COBOL constructor declaration on IBM.com/docs
7. Dart
8. Elixir
9. Fortran
10. Go
11. Groovy
12. Haskell
13. IBM REXX
- REXX constructor declaration on IBM.com/docs
14. IBM JCL
- JCL constructor declaration on IBM.com/docs
15. Java
16. JavaScript
17. Kotlin
18. PHP
19. PowerShell
20. Python
21. Ruby
22. Rust
23. Scala
24. Swift
25. Microsoft T-SQL
26. TypeScript
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