Delphi泛型EConversionError不能实例化类型
我想从JSON字符串响应中将数据反序列化到Delphi类中 - 有没有一种方法可以在Delphi中使用泛型来实现，所以我可以为每种不同类型的响应定义一个POCO类 - 在默认的Data属性中响应班？ 我在C＃中有更好的知识，并使用JavaScriptSerializer反序列化方法完成它，如下所示：
public Response<T> Get<T>(string methodUrl) where T: class
...
var _json_serializer = new JavaScriptSerializer();
_response = _json_serializer.Deserialize<Response<T>>(api_response);
...
public class Response
{
public bool Success { get; set; }
public string ErrorMessage { get; set; }
}
public class Response<T> : Response
{
public T Data;
public Response()
{
Data = default(T);
Success = false;
ErrorMessage = Settings.Default.errString;
}
}
我可以这样称呼它：
response = _webapi.Get<GetTestClass>(url_userinfo + sUserName);
internal class GetTestClass
{
public string DomainName { get; set; }
public int Code { get; set; }
}
德尔福有没有办法做到这一点？ 我使用函数GetUrlContent从Web API服务实现了Delphi10.1中的GET方法 - 我得到了有效的字符串响应。 所以我尝试了这个，它编译了，但是当它试图填充这个类时我得到了一个错误：
uses PPUserInfoDetails, APIRootClass;
var answer_class: TRootClass<TPPUserInfoDetails>;
Test_APIGet: string;
...
Test_APIGet := GetUrlContent(url_userinfo + sUserName);
answer_class:= TRootClass<TPPUserInfoDetails>.FromJsonString(Test_APIGet);
...
unit PPUserInfoDetails;
interface
type
TDataClass = class
private
FDisplayName: String;
FCode: Integer;
FRights: TArray<Integer>;
public
property DisplayName: String read FDisplayName write FDisplayName;
property Code: Integer read FCode write FCode;
property Rights: TArray<Integer> read FRights write FRights;
end;
implementation
end.
unit APIRootClass;
interface
uses Rest.Json , sysutils;
type
TRootClass<T> = class
private
FData: T;
FErrorMessage: String;
FSuccess: Boolean;
public
property Data: T read FData write FData;
property ErrorMessage: String read FErrorMessage write FErrorMessage;
property Success: Boolean read FSuccess write FSuccess;
constructor Create;
destructor Destroy; override;
function ToJsonString: string;
class function FromJsonString(AJsonString: string): TRootClass<T>;
end;
implementation
constructor TRootClass<T>.Create;
begin
inherited;
FData := Default(T);
end;
destructor TRootClass<T>.Destroy;
begin
freeandnil(FData);
inherited;
end;
function TRootClass<T>.ToJsonString: string;
begin
result := TJson.ObjectToJsonString(self);
end;
class function TRootClass<T>.FromJsonString(AJsonString: string): TRootClass<T>;
begin
result := TJson.JsonToObject<TRootClass<T>>(AJsonString)
end;
我得到错误：项目Test.exe引发异常类EConversionError消息'内部：无法实例化类型APIRootClass.TRootClass'
当我在我的APINoGenerics单元中定义没有类似泛型的类时，我可以将数据反序列化为特定的格式类：
uses APINoGenerics;
var answer_class: TRootClass;
...
Test_APIGet := GetUrlContent(url_userinfo + sUserName);
answer_class := TRootClass.FromJsonString(Test_APIGet);
...
unit APINoGenerics;
interface
uses Rest.Json;
type
TDataClass = class
private
FDisplayName: String;
FCode: Integer;
FRights: TArray<Integer>;
public
property DisplayName: String read FDisplayName write FDisplayName;
property Code: Integer read FCode write FCode;
property Rights: TArray<Integer> read FRights write FRights;
end;
TRootClass = class
private
FData: TDataClass;
FErrorMessage: String;
FSuccess: Boolean;
public
property Data: TDataClass read FData write FData;
property ErrorMessage: String read FErrorMessage write FErrorMessage;
property Success: Boolean read FSuccess write FSuccess;
constructor Create;
destructor Destroy; override;
function ToJsonString: string;
class function FromJsonString(AJsonString: string): TRootClass;
end;
implementation
constructor TRootClass.Create;
begin
inherited;
FData := TDataClass.Create();
end;
destructor TRootClass.Destroy;
begin
FData.free;
inherited;
end;
function TRootClass.ToJsonString: string;
begin
result := TJson.ObjectToJsonString(self);
end;
class function TRootClass.FromJsonString(AJsonString: string): TRootClass;
begin
result := TJson.JsonToObject<TRootClass>(AJsonString)
end;
我希望能够在Delphi中使用泛型 - 所以我只想知道它是否可行以及如何？ 我试图寻找答案，但主要是遇到泛型不能在Delphi中运行的答案，所以我发布了这个答案，因为我没有看到这种类型的问题。
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