Question

I am thinking of using the builder pattern in C++ unit tests, to streamline the creation of input data for the code being tested.

In Java the common idiom seems to be to have the setters of the builder class return the (reference to) the builder object itself, so that multiple setters can be chained in a single line. E. g. the builder class could be defined like this:

// class builder 
public class Builder
{
  private Part1 part1;
  private Part2 part2;
  public Builder withPart1(Part1 p1);
  public Builder withPart2(Part2 p2);
};

And then used like this:

Builder b;
Part1 p1;
Part2 p2;
b.withPart1(p1).withPart2(p2);

The same effect can be achieved in C++ by having the setters return a reference to the builder object. However, I have not been able to find any examples of that on the web. Is this kind of “chaining” a common practice in C++? And if no, then why not?

Answer 1

Yes it’s a common practice, it’s called a “Fluent API”.

The canonical example:

while ((std::cin >> std::setbase(16) >> i >> s).getline(s2)) { ... }