如何一次正确释放Delphi中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;
  End;
var
  SomeRecord: TSomeRecord;
  SomeRecAr: array of 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，没有释放所有内容，当我重用 SomeRecord，这显然是不受欢迎的)我正在寻找一种方法来一次释放所有字段.我开始使用 string[255] 并使用 ZeroMemory()，这很好，直到它开始泄漏内存，那是因为我切换到 string.我仍然缺乏了解原因的知识，但这似乎与它的动态有关.我也在使用动态数组，所以我假设在任何动态上尝试 ZeroMemory() 都会导致泄漏.浪费了一天弄清楚这一点.我想我通过在 ZeroMemory() 之前在 SomeRecord 或 SomeRecAr 上使用 Finalize() 解决了这个问题，但我我不确定这是正确的方法还是只是我愚蠢.

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.

所以问题是:如何一次释放所有内容?是否存在一些我不知道的单一程序?

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?

换个说法，或者我愿意接受建议如何以不同的方式实现这些记录，所以我不需要在释放东西时进行复杂的尝试.我研究过使用 New() 创建记录，然后删除它 Dispose()，但我不知道调用后的变量是什么意思Dispose() 是未定义的，而不是 nil.另外，我不知道某种类型的变量(SomeRecord: TSomeRecord)与指向某个类型的变量(SomeRecord: ^TSomeRecord)有什么区别.我目前正在研究上述问题，除非有人能快速解释，否则可能需要一些时间.

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.

推荐答案

假设您有一个支持在记录上实现方法的 Delphi 版本，您可以像这样清除记录:

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;

如果你的编译器不支持 Default 那么你可以像这样简单地做同样的事情:

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;

<小时>

您可能更愿意避免在方法中改变值类型.在这种情况下，创建一个返回空记录值的函数，并将其与赋值运算符一起使用:

---

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;

<小时>

顺便说一句，我找不到 Default(TypeIdentifier) 的任何文档参考.有谁知道哪里可以找到吗?

---

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

至于您问题的第二部分，我认为没有理由不继续使用记录并使用动态数组分配它们.尝试自己管理生命周期更容易出错.

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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