ue4 C++ json數據的讀寫

這是改變恢復機制的json文件的例子 

//寫入

TSharedPtr < FJsonObject > RootObject = MakeShareable ( new FJsonObject );

TArray < TSharedPtr < FJsonValue > > PackagesThatCanBeRestored ;

TSharedPtr < FJsonObject > EntryObject = MakeShareable ( new FJsonObject );

EntryObject -> SetStringField ( TEXT ( "PackagePathName" ), TEXT ( "Temp/Untitled_1" ));

EntryObject -> SetStringField ( TEXT ( "AutoSavePath" ), TEXT ( "Temp/Untitled_1_Auto1.umap" ));

TSharedPtr < FJsonValue > EntryValue = MakeShareable ( new FJsonValueObject ( EntryObject ));

PackagesThatCanBeRestored . Add ( EntryValue );

RootObject -> SetBoolField ( TEXT ( "RestoreEnabled" ), true );

RootObject -> SetArrayField ( TEXT ( "Packages" ), PackagesThatCanBeRestored );

const FString Filename = FPaths :: GameSavedDir () / TEXT ( "Autosaves" ) / TEXT ( "PackageRestoreData.json" );

FArchive * const FileAr = IFileManager :: Get (). CreateFileWriter ( * Filename , FILEWRITE_EvenIfReadOnly );

if ( FileAr )

{

     TSharedRef < TJsonWriter < TCHAR , TPrettyJsonPrintPolicy < TCHAR > >> Writer = TJsonWriterFactory < TCHAR , TPrettyJsonPrintPolicy < TCHAR > >:: Create ( FileAr );  

     FJsonSerializer :: Serialize ( RootObject . ToSharedRef (), Writer );

     FileAr -> Close ();

}

// 讀取本地json文件

        const FString Filename = FPaths :: GameSavedDir () / TEXT ( "Autosaves" ) / TEXT ( "PackageRestoreData.json" );

        FArchive * const FileAr = IFileManager :: Get (). CreateFileReader ( * Filename );

        bool bJsonLoaded = false ;

        TSharedPtr < FJsonObject > RootObject = MakeShareable ( new FJsonObject );

       {

               TSharedRef < TJsonReader < TCHAR >> Reader = TJsonReaderFactory < TCHAR >:: Create ( FileAr );

               bJsonLoaded = FJsonSerializer :: Deserialize ( Reader , RootObject );

               FileAr -> Close ();

       }

        TMap < FString , FString > PackagesThatCanBeRestored ;

        TArray < TSharedPtr < FJsonValue > > PackagesThatCanBeRestoredArray = RootObject -> GetArrayField ( TEXT ( "Packages" ));

        int32 TiRen = RootObject -> GetIntegerField ( TEXT ( "TiRen" ));

        for ( auto It = PackagesThatCanBeRestoredArray . CreateConstIterator (); It ; ++ It )

       {

               TSharedPtr < FJsonObject > EntryObject = ( * It ) -> AsObject ();

               const FString PackagePathName = EntryObject -> GetStringField ( TEXT ( "PackagePathName" ));

               const FString AutoSavePath = EntryObject -> GetStringField ( TEXT ( "AutoSavePath" ));

               PackagesThatCanBeRestored . Add ( PackagePathName , AutoSavePath );

       }

        for ( auto It = PackagesThatCanBeRestored . CreateConstIterator (); It ; ++ It )

       {

               if ( TiRen == 1)

              {

                      EditorStartupMap = FPaths :: GameContentDir () / TEXT ( "Autosaves" ) / It -> Value ;

              }

               else

              {

                      EditorStartupMap = AutoSaveUtils :: GetAutoSaveDir () / It -> Value ;

              }

       }