Long delegation chains in C++

Question

This is definitely subjective, but I'd like to try to avoid it becoming argumentative. I think it could be an interesting question if people treat it appropriately.

In my several recent projects I used to implement architectures where long delegation chains are a common thing.

Dual delegation chains can be encountered very often:

bool Exists = Env->FileSystem->FileExists( "foo.txt" );

And triple delegation is not rare at all:

Env->Renderer->GetCanvas()->TextStr( ... );

Delegation chains of higher order exist but are really scarce.

In above mentioned examples no NULL run-time checks are performed since the objects used are always there and are vital to the functioning of the program and explicitly constructed when execution starts. Basically I used to split a delegation chain in these cases:

1) I reuse the object obtained through a delegation chain:

{ // make C invisible to the parent scope
   clCanvas* C = Env->Renderer->GetCanvas();
   C->TextStr( ... );
   C->TextStr( ... );
   C->TextStr( ... );
}

2) An intermediate object somewhere in the middle of the delegation chain should be checked for NULL before usage. Eg.

clCanvas* C = Env->Renderer->GetCanvas();

if ( C ) C->TextStr( ... );

I used to fight the case (2) by providing proxy objects so that a method can be invoked on non-NULL object leading to an empty result.

My questions are:

Is either of cases (1) or (2) a pattern or an antipattern?
Is there a better way to deal with long delegation chains in C++?

Here are some pros and cons I considered while making my choice:

Pros:

it is very descriptive: it is clear out of 1 line of code where did the object came from
long delegation chains look nice

Cons:

interactive debugging is labored since it is hard to inspect more than one temporary object in the delegation chain

I would like to know other pros and cons of the long delegation chains. Please, present your reasoning and vote based on how well-argued opinion is and not how well you agree with it.

Long delegation chains in C++

8 Answers