为通过元类实例化的实例序列化JSON对象 [英] Serializing JSON object for an instance instantiated through a metaclass

问题描述

SuperObject库有一个序列化对象的通用方法：

 类型
 TSomeObject = class 
 ... 
 end; 
 
 var 
 lJSON：ISuperObject; 
 lContext：TSuperRttiContext; 
 lSomeObject：TSomeObject; 
 begin 
 lSomeObject：= TSomeObject.Create; 
 lContext：= TSuperRttiContext.Create; 
 lJSON：= lContext.AsJson< TSomeObject>（lSomeObject）; 
  

但现在我正在处理元类实例。
这是对象结构：

  TJSONStructure = class（TObject）; 
 
 TReqBase = class（TJSONStructure）
 private 
 token：Int64; 
 public 
 end; 
 
 TReqLogin = class（TReqBase）
 private 
 username，
 password：String; 
 module：Integer; 
 public 
 end; 
 
 
类型
 TWebAct =（ttlogin，
 ttsignin）; 
 
 TReqClass = TReqBase类; 
 
 const 
 cWebActStructures：数组[TWebAct]的
记录
 RequestClass：TReqClass; 
 end 
 =（
 {ttlogin}（RequestClass：TReqLogin;），
 {ttsignin}（RequestClass：TReqSignIn;）//不在
以上的定义）; 
  

如果我现在尝试：

  var 
 lContext：TSuperRttiContext; 
 lJSON：ISuperObject; 
 lRequestClass：TReqClass; 
 lRequestBase：TReqBase; 
 begin 
 lRequestClass：= cWebActStructures [ttlogin] .RequestClass; 
 lRequestBase：= lRequestClass.Create; // TReqLogin类型的实例
 lContext：= TSuperRttiContext.Create; 
 lJSON：= lContext.AsJson< TReqBase>（lRequestBase）; 
  

我得到序列化的TReqBase： lJSON.AsString ='{token ：-12346789}'

我想让TReqLogin序列化。

试过：

• lContext.AsJson< TReqLogin>（lRequestBase）;将不起作用：不兼容的类型）[此外，我将不得不在我的例程中列出/处理所有可能的RequestClass类型]

lRequestBase.ClassType>（lRequestBase）都不是：E2531方法'AsJson'需要显式类型参数





任何方式我可以让我的lRequestBase序列化为TReqLogin，TReq ...而不必为它们全部编码？


解决方案

诀窍是不是创建一个 TSuperRttiContext 并自己调用它的AsJSOn方法，但要立即使用：

  lJSON：= RequestBase.ToJSON; 
  

然后，ToJSON方法将在幕后创建一个TSuperRttiContext并处理必要的转换。





非常感谢 Marjan 的帮助。




The SuperObject library has a generic method for serializing objects:

type
   TSomeObject = class
   ...
   end;

var
   lJSON       : ISuperObject;
   lContext    : TSuperRttiContext;
   lSomeObject : TSomeObject;
begin
   lSomeObject := TSomeObject.Create;
   lContext := TSuperRttiContext.Create;
   lJSON := lContext.AsJson<TSomeObject>(lSomeObject);

But now I'm dealing with metaclass instances.
This is the object structure:

TJSONStructure = class(TObject);

TReqBase = class(TJSONStructure)
private
   token: Int64;
public
end;

TReqLogin = class(TReqBase)
private
   username,
   password: String;
   module  : Integer;
public
end;


type
   TWebAct = (ttlogin,
              ttsignin);

TReqClass = class of TReqBase;

const
   cWebActStructures: Array[TWebAct] of
   record
      RequestClass : TReqClass;
   end
   = (
      { ttlogin  } (RequestClass: TReqLogin;),
      { ttsignin } (RequestClass: TReqSignIn;)     // Not in definitions above
     ); 

If I now try:

var
   lContext      : TSuperRttiContext;
   lJSON         : ISuperObject;
   lRequestClass : TReqClass;
   lRequestBase  : TReqBase;
begin
   lRequestClass := cWebActStructures[ttlogin].RequestClass;
   lRequestBase := lRequestClass.Create;     // instance of type TReqLogin
   lContext := TSuperRttiContext.Create;
   lJSON := lContext.AsJson<TReqBase>(lRequestBase);

I get the TReqBase serialized: lJSON.AsString = '{"token":-12346789}'
I want to have TReqLogin serialized.
Tried:

• lContext.AsJson< TReqLogin >(lRequestBase); won't work: incompatible types) [Besides, I would have to list/handle all possible RequestClass types in my routine]

• lContext.AsJson< lRequestBase.ClassType >(lRequestBase) neither: E2531 Method 'AsJson' requires explicit type argument(s)

Is there any way I can have my lRequestBase serialized as a TReqLogin, TReq... without having to code for them all?

解决方案

The trick is to not create a TSuperRttiContext and call its AsJSOn method myself, but to immediately use:

lJSON := RequestBase.ToJSON;

The ToJSON method will then create a TSuperRttiContext behind the scenes and handle the necessary conversions.

With a big thank you to Marjan for her help.

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