I have:

struct Foo {
  std::string first_name;
  std::string last_name;
  int age;
};

void DoFoo(const Foo& foo) {...}

I am writing tests for DoFoo and I would like to have default values for the members of Foo:

Foo default_foo = {.first_name = "John", .last_name = "Doe", .age = 42};

Then I have test testing different values, for example:

TestInvalidAge() {
  Foo my_foo = default_foo;
  my_foo.age = -1;
  ASSERT_FAILS(DoFoo(my_foo));
}

This syntax is annoying because it is verbose to keep copying Foo my_foo = default_foo in every test case. I was wondering if there is a way to get the following syntax to work:

struct TestFoo : public Foo {
  // Somehow set first_name to "John", last_name to "Doe" and age to 42.
}

TestInvalidAge() {
  ASSERT_FAILS(DoFoo(TestFoo{.age = -1}));
}

I don't know how to override and set the default values of base members.

I tried using a default constructor for TestFoo in https://onlinegdb.com/tHxetZ6u5 but then the TestFoo{.age = -1} syntax doesn't work and I have to write:

TestFoo my_foo = TestFoo();
my_foo.age = -1;

Which is exactly the syntax I was trying to avoid.

CodePudding user response：

You could initalize the base class in the TestFoo default constructor:

struct TestFoo : public Foo {
    TestFoo() : Foo{"John", "Doe", 42} {}

    // possibility to use a different age:    
    TestFoo(int Age) : TestFoo() {
        age = Age;
    }
};

Demo

Another option:

struct TestFoo : public Foo {
    TestFoo() : Foo{"John", "Doe", 42} {}
    TestFoo(const Foo& rhs) : TestFoo() {
        if(!rhs.first_name.empty()) first_name = rhs.first_name;
        if(!rhs.last_name.empty()) last_name = rhs.last_name;
        if(rhs.age) age = rhs.age;
    }
};

DoFoo(TestFoo{} = Foo{.age = -1});

Demo

CodePudding user response：

You can use in-class initializers. They are used as default when no other initializer is provided:

#include <string>
#include <iostream>
struct Foo {
  std::string first_name = "Peter";
  std::string last_name = "Parker";
  int age = 42;
};

int main(){
    Foo f{.age = 12};

    std::cout << f.first_name << " " << f.last_name;
}