delphi - 嵌套异常的正确方法是什么？ -使用Delphi

Question

假设我有三个（或更多）过程，如下所示，其中一些相互调用，其中任何一个都可能失败。

如果其中任何一个失败了，我希望“主”程序立即记录该失败并终止该程序。

在Delphi中用于将异常“回传”到每个先前过程调用的正确语法是什么？

如果有人可以帮助我获取主程序的Try / except块以识别出哪位失败，那就更好了！

这三个过程和主程序的示例伪代码如下所示。

（我认为我了解原理，与“提高”有关，但希望对实际语法和应该使用的代码有所帮助）

//////////////////////////////////////
Procedure DoProcA
begin
try
   begin
   {stuff};  //stuff that might fall
   end;
except
 on E : Exception do 
     begin 
     LogError ('error in A'); 
     end  //on E
end;//try

 //////////////////////////////////////

Procedure DoProcB
begin
try
  begin 
  Do ProcC;  //another proc that might fail
  {other stuff}
  end;
except
 on E : Exception do
     begin
     LogError ('error in B');
     end  //on E
end;//try

 //////////////////////////////////////

Procedure DoProcC
begin
try
  begin 
  {Do stuff}  //even more stuf fthat might fail
  end;
except
 on E : Exception do
     begin
     LogError ('error in C');
     end  //on E
end;//try

 //////////////////////////////////////

 //Main programo
 begin 
 try
    DoProcA;
    DoProcB;
    {other stuff}
 except
   {here I want to be able to do something like
    if failure of A, B or C then
       begin      
       LogError ('Failure somewhere in A, B or C');
       application.terminate;
       end;}
 end; //try
 end.

Answer 1

在记录每个异常后，让每个函数重新引发捕获的异常，例如：

Procedure DoProcA;
begin
  try
    {stuff};  //stuff that might fall
  except
    on E : Exception do 
    begin 
      LogError ('error in A'); 
      raise; // <-- here
    end;
  end;
end;

Procedure DoProcB;
begin
  try
    DoProcC;  //another proc that might fail
    {other stuff}
  except
    on E : Exception do
    begin
      LogError ('error in B');
      raise; // <-- here
    end;
  end;
end;

Procedure DoProcC;
begin
  try
    {Do stuff}  //even more stuff that might fail
  except
    on E : Exception do
    begin
      LogError ('error in C');
      raise; // <-- here
    end;
  end;
end;

begin 
  try
    DoProcA;
    DoProcB;
    {other stuff}
  except
    on E: Exception do
    begin
      LogError ('Failure somewhere in A, B or C');
      //Application.Terminate; // this is not useful unless Application.Run is called first
    end;
  end;
end.

如果要让主过程识别WHICH函数失败，则需要将该信息传递给异常链，例如：

type
  MyException = class(Exception)
  public
    WhichFunc: String;
    constructor CreateWithFunc(const AWhichFunc, AMessage: String);
  end;

constructor MyException.CreateWithFunc(const AWhichFunc, AMessage: String);
begin
  inherited Create(AMessage);
  WhichFunc := AWhichFunc;
end;

Procedure DoProcA;
begin
  try
    {stuff};  //stuff that might fall
  except
    on E : Exception do 
    begin 
      raise MyException.CreateWithFunc('DoProcA', E.Message); // <-- here
    end;
  end;
end;

Procedure DoProcB;
begin
  try
    DoProcC;  //another proc that might fail
    {other stuff}
  except
    on E : MyException do
    begin
      raise; // <-- here
    end;
    on E : Exception do
    begin
      raise MyException.CreateWithFunc('DoProcB', E.Message); // <-- here
    end;
  end;
end;

Procedure DoProcC;
begin
  try
    {Do stuff}  //even more stuff that might fail
  except
    on E : Exception do
    begin
      raise MyException.CreateWithFunc('DoProcC', E.Message); // <-- here
    end;
  end;
end;

begin 
  try
    DoProcA;
    DoProcB;
    {other stuff}
  except
    on E: MyException do
    begin
      LogError ('Failure in ' + E.WhichFunc + ': ' + E.Message);
    end;
    on E: Exception do
    begin
      LogError ('Failure somewhere else: ' + E.Message);
    end;
  end;
end.

要么：

type
  MyException = class(Exception)
  public
    WhichFunc: String;
    constructor CreateWithFunc(const AWhichFunc, AMessage: String);
  end;

constructor MyException.CreateWithFunc(const AWhichFunc, AMessage: String);
begin
  inherited Create(AMessage);
  WhichFunc := AWhichFunc;
end;

Procedure DoProcA;
begin
  try
    {stuff};  //stuff that might fall
  except
    on E : Exception do 
    begin 
      raise MyException.CreateWithFunc('DoProcA', E.Message); // <-- here
    end;
  end;
end;

Procedure DoProcB;
begin
  try
    DoProcC;  //another proc that might fail
    {other stuff}
  except
    on E : Exception do
    begin
      Exception.RaiseOuterException(MyException.CreateWithFunc('DoProcB', E.Message)); // <-- here
    end;
  end;
end;

Procedure DoProcC;
begin
  try
    {Do stuff}  //even more stuff that might fail
  except
    on E : Exception do
    begin
      raise MyException.CreateWithFunc('DoProcC', E.Message); // <-- here
    end;
  end;
end;

var
  Ex: Exception;
begin 
  try
    DoProcA;
    DoProcB;
    {other stuff}
  except
    on E: Exception do
    begin
      Ex := E;
      repeat
        if Ex is MyException then
          LogError ('Failure in ' + MyException(Ex).WhichFunc + ': ' + Ex.Message)
        else
          LogError ('Failure somewhere else: ' + Ex.Message);
        Ex := Ex.InnerException;
      until Ex = nil;
    end;
  end;
end.