如何在Delphi中正确释放包含各种类型的记录？ [英] How to properly free records that contain various types in Delphi at once?

问题描述

  type 
 TSomeRecord = Record 
 field1：integer; 
 field2：string; 
 field3：boolean; 
结束; 
 var 
 SomeRecord：TSomeRecord; 
 SomeRecAr：数组的TSomeRecord; 
  

这是我所拥有的最基本的例子，因为我想重用 SomeRecord （某些字段保持为空，并且在我重新使用 SomeRecord 之前，不会释放所有的字段，这显然是不需要的）我正在寻找一种方式来一次释放所有的领域。我已经开始使用 string [255] ，并使用 ZeroMemory（），这是很好，直到它开始泄漏内存，那是因为我切换到 string 。我仍然缺乏了解为什么的知识，但它似乎与动态有关。我也使用动态数组，所以我假设在任何动态的情况下尝试 ZeroMemory（）会导致泄漏。有一天浪费了。我想我通过使用 Finalize（）在 SomeRecord 或 SomeRecAr before ZeroMemory（），但我不知道这是正确的方法还是只是我是愚蠢的。

$ b $所以问题是：如何一次释放所有东西？有没有一些单一的程序存在，我不知道？

另一方面，我可以建议如何不同地实现这些记录开始，所以我不需要做复杂的尝试释放的东西。我已经研究了用 New（）创建记录，然后摆脱它 Dispose（），但我有当调用 Dispose（）之后的变量是未定义的，而不是nil，这意味着什么。另外，我不知道某种类型的变量（ SomeRecord：TSomeRecord ）与指向类型的变量（ SomeRecord：^ TSomeRecord ）。我正在研究上述问题，除非有人可以快速解释，否则可能需要一些时间。

解决方案

假设您有一个支持在记录上实现方法的Delphi版本，您可以清除以下记录：

 键入
 TSomeRecord = record 
 field1：integer; 
 field2：string; 
 field3：boolean; 
程序清除; 
结束
 
程序TSomeRecord.Clear; 
 begin 
自我：=默认（TSomeRecord）; 
结束
  

如果您的编译器不支持默认那么你可以这样做：

  procedure TSomeRecord.Clear; 
 const 
默认值：TSomeRecord =（）; 
 begin 
自我：=默认; 
结束
  

---

您可能希望避免将值类型突变一个方法。在这种情况下，创建一个返回空记录值的函数，并使用赋值运算符：

 键入
 TSomeRecord = record 
 // fields go here 
 class function Empty：TSomeRecord;静态的; 
结束
 
类函数TSomeRecord.Empty：TSomeRecord; 
 begin 
结果：=默认值（TSomeRecord）; 
结束
 
 .... 
 
值：= TSomeRecord.Empty; 
  

---

除此之外，我找不到任何文档参考对于 Default（TypeIdentifier）。有谁知道在哪里可以找到？

---

至于你的问题的第二部分，我看不出没有理由不继续使用记录，并使用动态数组进行分配。尝试自己管理一生的时间更容易出错。

type
  TSomeRecord = Record
    field1: integer;
    field2: string;
    field3: boolean;
  End;
var
  SomeRecord: TSomeRecord;
  SomeRecAr: array of TSomeRecord;

This is the most basic example of what I have and since I want to reuse SomeRecord (with certain fields remaining empty, without freeing everything some fields would be carried over when I'm reusing SomeRecord, which is obviously undesired) I am looking for a way to free all of the fields at once. I've started out with string[255] and used ZeroMemory(), which was fine until it started leaking memory, that was because I switched to string. I still lack the knowledge to get why, but it appears to be related to it being dynamic. I am using dynamic arrays as well, so I assume that trying ZeroMemory() on anything dynamic would result in leaks. One day wasted figuring that out. I think I solved this by using Finalize() on SomeRecord or SomeRecAr before ZeroMemory(), but I'm not sure if this is the proper approach or just me being stupid.

So the question is: how to free everything at once? does some single procedure exist at all for this that I'm not aware of?

On a different note, alternatively I would be open to suggestions how to implement these records differently to begin with, so I don't need to make complicated attempts at freeing stuff. I've looked into creating records with New() and then getting rid of it Dispose(), but I have no idea what it means when a variable after a call to Dispose() is undefined, instead of nil. In addition, I don't know what's the difference between a variable of a certain type (SomeRecord: TSomeRecord) versus a variable pointing to a type (SomeRecord: ^TSomeRecord). I'm looking into the above issues at the moment, unless someone can explain it quickly, it might take some time.

解决方案

Assuming you have a Delphi version that supports implementing methods on a record, you could clear a record like this:

type
  TSomeRecord = record
    field1: integer;
    field2: string;
    field3: boolean;
    procedure Clear;
  end;

procedure TSomeRecord.Clear;
begin
  Self := Default(TSomeRecord);
end;

If your compiler doesn't support Default then you can do the same quite simply like this:

procedure TSomeRecord.Clear;
const
  Default: TSomeRecord=();
begin
  Self := Default;
end;

---

You might prefer to avoid mutating a value type in a method. In which case create a function that returns an empty record value, and use it with the assignment operator:

type
  TSomeRecord = record
    // fields go here
    class function Empty: TSomeRecord; static;
  end;

class function TSomeRecord.Empty: TSomeRecord;
begin
  Result := Default(TSomeRecord);
end;

....

Value := TSomeRecord.Empty;

---

As an aside, I cannot find any documentation reference for Default(TypeIdentifier). Does anyone know where it can be found?

---

As for the second part of your question, I see no reason not to continue using records, and allocating them using dynamic arrays. Attempting to manage the lifetime yourself is much more error prone.

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