Local function
A local function is a named function declared within another function or local scope and accessible within that enclosing lexical context.
Kotlin in Action, 2E
A local function is a function declared within another function or local scope rather than at the top level or as a class member.
- How it is used
- Structures function-specific helper logic while avoiding duplicated validation and unnecessary class methods.
- How deep it goes
- Explains nesting, scope, duplication removal, and captured parameters, then stops at an extension-function alternative.
- Examples
- Uses saveUser validation for empty name and address fields, first passing User explicitly and then capturing it.
- What you can do after
- Apply it in Kotlin to organize function-local validation and remove small repetitions without expanding a class API.
React Quickly, Second Edition
A local function is a function defined within another function and accessible within that enclosing function's lexical scope.
- How it is used
- Converts class methods that depend on component-local information into functional-component code.
- How deep it goes
- Compares pure and local functions with concrete calls and JSX, but does not develop deeper implementation internals.
- Examples
- Uses an Image component whose local getImageSource function builds a Picsum image URL from index.
- What you can do after
- Apply it via functional components to retain compact calls while accessing component-local values.
Read how React Quickly, Second Edition explains local function →
Related concepts
- let keywordused by · A let construct is a language feature that introduces a name binding associating an identifier with a value or expression.
- functionkind of · A function is a callable program unit that performs an operation, may accept inputs, and can produce a result or side effect.
- class methodalternative to · A class method is a method associated with a class rather than a particular instance and invoked through a class or class-related object.
- inner classcontrasts with · An inner class is a class declared within another class whose instances are associated with an instance of the enclosing class.
- scopecontrasts with · Scope is the region of a program in which names are visible and can be resolved according to the language’s lookup rules.
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