The Tool Desk
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Define an anonymous method type and assign a function
Start by declaring the signature the callable value must match. The reference to syntax creates a managed method-reference type; it is not the same thing as a traditional procedure of object pointer.
type
TIntToInt = reference to function(X: Integer): Integer;
var
DoubleIt: TIntToInt;
begin
DoubleIt := function(X: Integer): Integer
begin
Result := X * 2;
end;
end;Once assigned, DoubleIt can be invoked like a function. Anonymous methods are useful when a small piece of behavior belongs at its point of use, rather than needing a separately named routine.
Pass behavior into a function
A higher-order function accepts another function or procedure as an argument, or returns one. This lets one algorithm use different policies without creating a separate named method for each variation.
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type
TStringTransform = reference to function(const S: string): string;
function ApplyTransform(const S: string; F: TStringTransform): string;
begin
Result := F(S);
end;Callers can pass an anonymous method directly or store it in a variable of type TStringTransform before passing it. Embarcadero’s Anonymous Methods in Delphi documentation demonstrates the same pattern with a function parameter.
Return a closure that remembers a value
A function can return a method reference. In this example, MakeAdder returns a function that adds the value of Y to its argument:
type
TFuncOfInt = reference to function(X: Integer): Integer;
function MakeAdder(Y: Integer): TFuncOfInt;
begin
Result := function(X: Integer): Integer
begin
Result := X + Y;
end;
end;Conceptually, MakeAdder(20)(22) produces 42. The returned function remains able to access Y after MakeAdder has returned. The official documentation uses this closure pattern in its MakeAdder example.
Understand what a closure captures
Delphi captures variable storage from the defining scope, not an immutable snapshot of each variable’s value. If the outer variable changes while a method reference remains alive, invoking the anonymous method reads the changed variable.
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- Capture only the state the callback needs; avoid capturing an object that also retains the callback unless you have a plan to break the ownership cycle.
- If a closure reads or writes state shared with other code, reason about synchronization separately. Capturing a variable does not make concurrent access thread-safe.
Use anonymous methods in Delphi code
Parameterize a generic-list sort
A sorting routine can accept a comparison policy as a method reference, allowing the same sorting operation to order values differently. For a generic collection, define the callback signature required by the collection’s sort API and provide the comparison behavior as an anonymous method when that API accepts the corresponding method-reference type. Verify the exact signature in the documentation for your Delphi version and collection type.
Represent a callback or event
A property or API designed to hold a reference to type can use an anonymous method as its callback. This is convenient when the response is short and local to the registration site. It does not mean an anonymous method can be assigned to every Delphi event type: traditional events commonly use method-pointer types, which have different type and lifetime semantics.
Provide work to parallel operations
Parallel-library patterns can accept anonymous methods for operations such as Parallel For loops, tasks, and futures. The callback syntax can keep the work close to the operation that schedules it. If multiple workers access captured state, protect that state using an appropriate synchronization strategy; a closure is a way to package behavior, not a concurrency guarantee. The Embarcadero Academy Anonymous Methods in Delphi course includes sorting generic collections, threading, Parallel For, tasks, and futures.
Choose between a closure, a routine, and a method pointer
| Choice | Captures outer state? | Lifetime model | Best fit |
|---|---|---|---|
Anonymous method (reference to) |
Yes | Managed and reference-counted | Inline policies, callbacks, closures, and higher-order utilities |
| Named routine | No implicit closure capture | Normal routine rules | Reusable, discoverable business logic |
Method pointer (procedure of object) |
No closure frame | Unmanaged pointer semantics | Traditional object events and stable method callbacks |
Anonymous methods cannot be assigned to regular method-pointer types: Embarcadero documents method references as managed types and method pointers as unmanaged. Use the callback type the receiving API actually declares, rather than assuming the two forms are interchangeable.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Check compiler and platform support
RAD Studio’s language feature matrix lists anonymous methods/closures and generics as supported language and runtime features. That establishes current feature support, but it is not a complete version-by-version behavior or performance matrix. Check the target compiler and platform—especially when supporting multiple Delphi releases—before relying on identical behavior or performance across targets.
For a deeper language reference, Marco Cantù’s Object Pascal Handbook product page describes a 500-page ebook for Delphi 11 Alexandria. Its version label makes it a useful reference for that generation, not proof of every detail in later releases.
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