传递值来同步线程 [英] Passing value to synchronize thread

问题描述

我是新来的线程，所以我一直在尝试几个小时（我使用XE4），

I'm new to thread, so i've been trying with this for hours (i'm using XE4),

我有一个简单的线程

i have a simple thread

type
  TSendThread = class(TThread)
  private
  public
    procedure proc(const s : string);
  protected
    procedure Execute; override;
  end;

  procedure TSendThread.proc(const S: String);
  begin
    showmessage(s);
  end;

现在，以我的主要形式，我想用

Now, in my main form, i want to call that "proc" with :

procedure TForm1.Button1Click(Sender: TObject);
var
  t : TSendThread;
begin
    t := TSendThread.create(true);
    t.Synchronize(nil, t.proc('foo'));
end;

但是每当我尝试编译，我得到：

But whenever i try t compile that i get :

没有重载版本的同步，可以使用这些参数调用

There is no overloaded version of 'Synchronize' that can be called with these arguments

对我来说没有意义，因为当我从proc中删除S参数时，它工作正常。

that does not make sense (to me) because when i remove the "S" parameter from "proc" it works fine.

推荐答案

查看 TThread.Synchronize（）的各种声明。您正在尝试调用采用 TThreadMethod 作为输入的版本。 TThreadMethod 是无参数的：

Look at the various declarations of TThread.Synchronize(). You are trying to call the version that takes a TThreadMethod as input. TThreadMethod is parameter-less:

TThreadMethod = procedure of object;

这就是为什么只传递 t.Proc 作品，但通过 t.Proc（'foo'）不。

That is why passing just t.Proc works but passing t.Proc('foo') does not.

就是说，你是完全滥用 TThread.Synchronize（）。您不需要创建一个 TThread 对象，以便使用静态版本的 Synchronize（）。如果您创建一个 TThread 对象，请使其实际执行某些操作，如下所示：

With that said, you are completely misusing TThread.Synchronize(). You don't need to create a TThread object in order to use the static version of Synchronize(). And if you do create a TThread object, make it actually do something, like this:

type
  TSendThread = class(TThread)
  public
    fStr: String;
    procedure DoProc;
    procedure Proc(const S: string);
  protected
    procedure Execute; override;
  end;

  procedure TSendThread.Execute;
  begin
    Proc('foo');
  end;

  procedure TSendThread.Proc(const S: string);
  begin
    fStr := S;
    Synchronize(DoProc);
  end;

  procedure TSendThread.DoProc;
  begin
    ShowMessage(fStr);
  end;

procedure TForm1.Button1Click(Sender: TObject);
var
  t : TSendThread;
begin
  t := TSendThread.Create(False);
  t.WaitFor;
  t.Free;
end;

但是，由于您使用的是XE4， Synchronize（）还支持匿名过程，这将在本示例中完全消除您的 TSendThread 类，例如：

However, because you are using XE4, Synchronize() also supports anonymous procedures as well, which would eliminate your TSendThread class completely in this example, eg:

procedure TForm1.Button1Click(Sender: TObject);
begin
  TThread.Synchronize(nil,
    procedure
    begin
      ShowMessage('foo');
    end
  );
end;

更新：给出关于您真正想要做什么的新信息线程，你需要像这样改为：

Update: given new info about what you REALLY want to do with your thread, you need to go about it like this instead:

type
  TSendThread = class(TThread)
  private
    fURL, fMethod, fParam: string;
  protected
    procedure Execute; override;
  public
    constructor Create(aURL, aMethod, aParam: string);
  end;

constructor TSendThread.Create(aURL, aMethod, aParam: string);
begin
  inherited Create(False);
  fURL := aUrl;
  fMethod := aMethod;
  fParam := aParam;
end;

procedure TSendThread.Execute;
begin
  // use fURL, fMethod, and fParam as needed...
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  t : TSendThread;
begin
  t := TSendThread.Create('url', 'method', 'param');
  ...
end;

或像这样：

type
  TSendThread = class(TThread)
  private
    fURL, fMethod, fParam: string;
    procedure GetValues;
  protected
    procedure Execute; override;
  end;

procedure TSendThread.GetValues;
begin
  fURL := ...;
  fMethod := ...;
  fParam := ...;
end;

procedure TSendThread.Execute;
begin
  Synchronize(GetValues);
  // use fURL, fMethod, and fParam as needed...
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  t : TSendThread;
begin
  t := TSendThread.Create(False);
  ...
end;

这篇关于传递值来同步线程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！