[C++]How To Save Array Of Structs

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1

Hey guys. I have a struct A that stores transform, softclass ptr, string, and TArray. I am using the ObjectAndNameAsStringProxyArchive. I am trying to save an array of struct A but can’t figure out how to. I have a struct B that holds the array and a string. Once all the struct A’s are added to the array in struct B, I want to save struct B to a file. Problem is I can’t figure out how to do this. I can save a single struct A by writing it’s TArray to file but that won’t work in the case of struct B. How would I save struct B to a file? (I already have a file path). I can provide more info if needed. Thank you in advance!

2

I figured it out. I needed to add a TArray to struct B to act as the bytestream. In struct B, I overloaded the << operator to save to my archive. And then to save, I just set the array, created a FMemoryWriter with the bytestream, and then created the archive and using the overloaded << operator, I saved to the archive. And finally, I wrote the bytestream to the file.

3

Hi! You can do this is several steps:

  1. In all classes that you want to serialize or deserialize you should define << OPERATOR

    USTRUCT(BlueprintType)
    class SomeClass: public UObject {
    GENERATED_BODY()

    … // All you props, for example Prop1, Prop2, etc

    friend FArchive& operator<<(FArchive& Ar, SomeClass& objToSerialize) {
    Ar << objToSerialize.Prop1;
    Ar << objToSerialize.Prop2;
    …
    return Ar;
    }
    };

  2. Saving data in file is simple as this

    void Save(SomeClass& objToSave) {

     FString filePath = FPaths::ProjectSavedDir() + "mydata.sav"; // file path you want

 FBufferArchive SaveData;
 SaveData << objToSave;
 FFileHelper::SaveArrayToFile(SaveData, *filePath);

 SaveData.FlushCache();
 SaveData.Empty();

    }

And some additional remarks:

  • you can easily serialize and deserialize TArray if T is serializable in the sense of 1)
  • serialize and deserialize in Unreal both are implemented with the same << OPERATOR. The thing is that some FArchive child classes save data and others - load. For example, FBufferArchive saves data from classes to stream (same as std::cout), while FMemoryReader can read data from stream to variables (same as std::cin)
  • To serialize and deserialize class B that has class A prop, work it out with class A and after that you can start with class B
  • UClass refs (TSubclassOf) can be serialized and deserialized by GetPathName() and StaticLoadClass(…) methods respectively
1 Like
4

Sorry, but I forgot to tell that I figured it out an hour ago. I’ll post the answer shortly.