[silverweed]

This Pull request:

Adds the ability of storing object titles when writing objects to RFile.

CAVEATS/to be discussed:

• TObjects are not treated specially, meaning that if your TObject has a title it won't be used automatically when storing the object (for that you need an explicit rfile->Put("obj", obj, obj->GetTitle()));
• Doing a rfile->Put("obj", myTObject, "My Title") will not set myTObject's title, but only its key's. This means that this potentially unexpected behavior will occur:

rfile->Put("myobj", myobj, "obj title");
auto myobj2 = rfile->Get<MyTObj>("myobj");
cout << myobj2->GetTitle() << "\n";  // prints ""

In order to retrieve the object's title you'd need to do it from the key:

auto keyInfo = rfile->GetKeyInfo("myobj").value();
cout << keyInfo.GetTitle() << "\n"; // prints "obj title"

To be discussed: are we ok with this behavior or do we want bespoke TObject/TNamed code in the implementation to mitigate these pitfalls?

[github-actions]

Test Results

    23 files      23 suites   3d 18h 36m 4s ⏱️
 3 895 tests  3 890 ✅ 0 💤 5 ❌
79 613 runs  79 608 ✅ 0 💤 5 ❌

For more details on these failures, see this check.

Results for commit df0866b.

♻️ This comment has been updated with latest results.

[jblomer]

I am actually more in favor of special behavior for TObject arguments that understands/uses their title member. We can discuss.

[hageboeck]

To be discussed: are we ok with this behavior or do we want bespoke TObject/TNamed code in the implementation to mitigate these pitfalls?

I tend to lean towards bespoke code. Should we discuss this in a (zoom) meeting with a few people?

[silverweed]

I am actually more in favor of special behavior for TObject arguments that understands/uses their title member. We can discuss.

I tend to lean towards bespoke code. Should we discuss this in a (zoom) meeting with a few people?

To be clear:

1. I can add the following behavior:

// since a title wasn't passed to `Put`, the object key's title is implicitly set to `myTNamed.GetTitle()`
rfile->Put("myTNamed", myTNamed); 

2. but I cannot add the following:

TNamed myTNamed;
// `myTNamed`'s title gets set to `"my title"`
rfile->Put("myTNamed", myTNamed, "my title");

This is because myTNamed is passed as a const &, so it cannot be modified.

Disadvantage of implementing 1: if we want a concise way to tell rfile "ignore this object's title and save it without title" for TNamed objects we need to implement an overload of Put that allows distinguishing between passing an empty title and no title at all (because currently "no title passed" is the same as "empty title passed")

EDIT: for reference, see latest commit.

[pcanal]

rfile->Put("myTNamed", myTNamed, "my title");
This is because myTNamed is passed as a const &, so it cannot be modified.

I am confused why this is an issue? rfile->Put("myTNamed", myTNamed); use the first parameter whether or not it matches the name of the TNamed, so why wouldn't Put("myTNamed", myTNamed, "my title"); use the third parameter as a title whether or not it matches the TNamed's title?

And since we are overloading, can't we also support:

Put(const TNamed &obj) { PutInternal(obj.GetName(), obj, obj.GetTitle()); } 

[silverweed]

rfile->Put("myTNamed", myTNamed, "my title");
This is because myTNamed is passed as a const &, so it cannot be modified.

I am confused why this is an issue? rfile->Put("myTNamed", myTNamed); use the first parameter whether or not it matches the name of the TNamed, so why wouldn't Put("myTNamed", myTNamed, "my title"); use the third parameter as a title whether or not it matches the TNamed's title?

It's not really an issue, unless the user expects the object's name/title to be changed by the Put call (which they shouldn't expect given the signature).

And since we are overloading, can't we also support:

Put(const TNamed &obj) { PutInternal(obj.GetName(), obj, obj.GetTitle()); } 

I actually might like this option better than my current one. With this we could have:

• the "regular" overload of Put(string_view path, const T &obj, string_view title = "") which sets the title to whichever string the user passes/doesn't pass (no special treatment of TNamed)
• the TNamed-specific overload of Put(const TNamed &obj) which does what you wrote.

[silverweed]

Replaced by #23807