通过修改FObjectInitializer参数, 来修改默认创

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我们在这里设置要重载的子类:UBaseCharacterMovementComp

其实这个函数(SetDefaultSubobjectClass)就是把UBaseCharacterMovementComp对应的UClass放入ComponentOverrides中

    template<class T>
    FObjectInitializer const& SetDefaultSubobjectClass(FName SubobjectName) const
    {
        AssertIfSubobjectSetupIsNotAllowed(*SubobjectName.GetPlainNameString());
        ComponentOverrides.Add(SubobjectName, T::StaticClass(), *this);
        return *this;
    }

在构造函数中调用CreateDefaultSubobject时候, 会自动触发函数重载.

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从ComponentOverrides取出UBaseCharacterMovementComp, 然后创建:

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调用堆栈:

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这里还要补充一句:
FUObjectThreadContext维护了一个全局堆栈, 用于保存当前的FObjectInitializer

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使用的时候直接取栈顶的FObjectInitializer

UObject* UObject::CreateDefaultSubobject(FName SubobjectFName, UClass* ReturnType, UClass* ClassToCreateByDefault, bool bIsRequired, bool bAbstract, bool bIsTransient)
{
    FObjectInitializer* CurrentInitializer = FUObjectThreadContext::Get().TopInitializer();
    UE_CLOG(!CurrentInitializer, LogObj, Fatal, TEXT("No object initializer found during construction."));
    UE_CLOG(CurrentInitializer->Obj != this, LogObj, Fatal, TEXT("Using incorrect object initializer."));
    return CurrentInitializer->CreateDefaultSubobject(this, SubobjectFName, ReturnType, ClassToCreateByDefault, bIsRequired, bAbstract, bIsTransient);
}