Skip to content
This repository was archived by the owner on Feb 24, 2025. It is now read-only.

TEnumerator

Jump to bottom
Ivan Semenkov edited this page Feb 13, 2021 · 2 revisions

Table of contents

About

Class adds counter to an iterable object and returns it like in a Python language.

uses utils.enumerate; type generic TEnumerator<V; Iterator> = class

Iterator is a forward iterator implemented object.

TOptionalValue

If macro {$USE_OPTIONAL} is defined, then all methods return a TOptionalValue wrapper, otherwise V.

uses utils.optional; type TOptionalValue = {$IFDEF FPC}specialize{$ENDIF} TOptional<V>;

Create

A new enumerator can be created by call its constructor.

constructor Create (AIterator : Iterator; AStartIndex : Integer = 0);

AIterator is a forward iterator implemented object.

AStartIndex is counter start index value.

Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); FreeAndNil(enumerator); FreeAndNil(list); end;

Iterate

It is possible to iterate for TEnumerator values using in operator. Each value would present as TEnumerator.TIterator object.

uses utils.enumerate; type generic TEnumerator<V; Iterator> = class type TIterator = class end;
Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; iterator : TIntegerListEnumerator.TIterator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); for iterator in enumerator do ; FreeAndNil(enumerator); FreeAndNil(list); end;

FirstEntry

Retrive the first entry.

function FirstEntry : TIterator;
Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; iterator : TIntegerListEnumerator.TIterator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); iterator := enumerator.FirstEntry; while iterator.HasValue do begin	iterator := iterator.Next; end; FreeAndNil(enumerator); FreeAndNil(list); end;

TIterator

HasValue

Return true if iterator has correct value.

function HasValue : Boolean;
Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; iterator : TIntegerListEnumerator.TIterator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); for iterator in enumerator do begin if iterator.HasValue then ; end; FreeAndNil(enumerator); FreeAndNil(list); end;
Next

Retrieve the iterator for next entry.

function Next : TIterator;
Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; iterator : TIntegerListEnumerator.TIterator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); for iterator in enumerator do begin if iterator.Next.HasValue then ; end; FreeAndNil(enumerator); FreeAndNil(list); end;
Value

To get value use Value property.

property Value : {$IFNDEF USE_OPTIONAL}V{$ELSE}TOptionalValue{$ENDIF};
Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; iterator : TIntegerListEnumerator.TIterator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); for iterator in enumerator do begin writeln(iterator.Value); end; FreeAndNil(enumerator); FreeAndNil(list); end;
Index

Get current item index.

property Index : Integer;
Example
uses container.list, utils.functor, utils.enumerate; type TIntegerList = {$IFDEF FPC}specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; TIntegerListEnumerator = {$IFDEF FPC}specialize{$ENDIF} TEnumerator<Integer, TIntegerList.TIterator>; var list : TIntegerList; enumerator : TIntegerListEnumerator; iterator : TIntegerListEnumerator.TIterator; begin list := TIntegerList.Create; enumerator := TIntegerListEnumerator.Create(list.FirstEntry, 0); for iterator in enumerator do begin writeln(iterator.Value); writeln(iterator.Index); end; FreeAndNil(enumerator); FreeAndNil(list); end;
Clone this wiki locally