First-class message

In <a href="/facts/Object-oriented_programming/TxNMEcao">object-oriented programming</a>, a programming language is said to have first-class messages or dynamic messages if in a <a href="/facts/Method_call/8kAXxVYs">method call</a> not only the receiving <a href="/facts/Object_(object-oriented_programming)/eX99dtAw">object</a> and parameter list can be varied dynamically (i.e. bound to a variable or computed as an expression) but also the specific method invoked.
Typed object-oriented programming languages, such as <a href="/facts/Java_(programming_language)/9ScgFyAL">Java</a> and <a href="/facts/C%252B%252B/Et0F2qn9">C++</a>, often do not support first-class methods. <a href="/facts/Smalltalk/Ru2UPVDE">Smalltalk</a> only support them in an untyped way. In <a href="/facts/Objective-C/5mM557BW">Objective-C</a> (<a href="/facts/Cocoa_(API)/p10p5aFI">Cocoa</a>), you can use NSInvocation to represent first-class messages in a way that is aware of the types at runtime; however, safe use still relies on the programmer.
Some theoretical progress has been made to support first-class messages in a <a href="/facts/Type_safety/WxmEKq8R">type-safe</a> manner, but none of the proposed systems has been implemented in a programming language, possibly due to their complexity.

First-class message open-in-new

First-class message