如何将另一个函数返回的函数分配给函数变量?结果而不是生成函数本身 [英] How to assign a function, returned by another function, to a function variable? The result rather than the generating function itself

问题描述

一个函数正在返回一个匿名函数.我想将结果分配给一个变量.但是，编译器认为我正在尝试分配函数，而不是函数的结果.我该如何解决?

A function is returning an anonymous function. I would like to assign the result to a variable. However the compiler thinks that I am trying to assign the function and not the result of the function. How can I resolve this?

program Project9;

{$APPTYPE CONSOLE}

type
  TMyEvent = reference to function: string;

var
  v1: TMyEvent;

function GetHandler: TMyEvent;
begin
  Result := function: string
            begin
              Result := '';
            end;
end;

begin
  v1 := GetHandler;  // <- Incompatible types: 'TMyEvent' and 'Procedure'
end.

注意:我确实有一种解决方法，但我希望可以在不引入包装器的情况下解决此问题:

Note: I do have a workaround but I hope that this problem can be solved without introducing a wrapper:

program Project9;

{$APPTYPE CONSOLE}

type
  TMyEvent = reference to function: string;

  TWrapper = record
    FHandler: TMyEvent;
  end;

var
  v1: TMyEvent;

function GetHandler: TWrapper;
begin
  Result.FHandler := function: string
                     begin
                       Result := '';
                     end;
end;

begin
  v1 := GetHandler.FHandler;  // <- works

这并非特定于匿名函数或任何特殊类型的函数:对于返回该函数的任何函数都是实际的，甚至在第一个Delphi到达之前，它在Turbo Pascal中都是相同的.

推荐答案

如果您的匿名方法/函数是无参数的，则必须分配();

If your anonymous methods/functions are paramless, you must assign with ();

v1 := GetHandler();

在没有括号的情况下，Delphi将尝试将功能分配给变量.括号告诉它调用该函数并将函数结果分配给该变量.

Without the parentheses Delphi will try to assign the function to the variable. The parens tell it to invoke the function and assign the function result to the variable.

这篇关于如何将另一个函数返回的函数分配给函数变量?结果而不是生成函数本身的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！