Editing Class invariant (section)

==Programming language support==

===Assertions===

Common programming languages like Python,<ref>[https://docs.python.org/3/reference/simple_stmts.html#grammar-token-assert-stmt Official Python Docs, ''assert statement'']</ref> PHP,<ref>{{Cite web|title=PHP assert function|url=https://www.php.net/manual/en/function.assert.php|url-status=live|archive-url=https://web.archive.org/web/20010321003333/http://www.php.net:80/manual/en/function.assert.php |archive-date=2001-03-21 }}</ref> JavaScript,{{citation needed|date=February 2021}} C++ and Java support [[Assertion (computing)|assertions]] by default, which can be used to define class invariants. A common pattern to implement invariants in classes is for the constructor of the class to throw an exception if the invariant is not satisfied. Since methods preserve the invariants, they can assume the validity of the invariant and need not explicitly check for it.

===Native support===

The class invariant is an essential component of [[design by contract]]. So, programming languages that provide full [[Design by contract#Languages with native support|native support for design by contract]], such as [[Eiffel (programming language)|Eiffel]], [[Ada (programming language)|Ada]], and [[D (programming language)|D]], will also provide full support for class invariants.

===Non-native support===

For [[C++]], the [[Loki (C++)|Loki Library]] provides a framework for checking class invariants, static data invariants, and exception safety.

For Java, there is a more powerful tool called [[Java Modeling Language]] that provides a more robust way of defining class invariants.