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Add another example for generators

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horenmar committed Feb 26, 2019
1 parent 29b3b7a commit 5bf6e473810d0df443024a3cafea5ab301e00e91
Showing with 56 additions and 0 deletions.
  1. +1 −0 docs/list-of-examples.md
  2. +54 −0 examples/301-Gen-MapTypeConversion.cpp
  3. +1 −0 examples/CMakeLists.txt
@@ -15,6 +15,7 @@
- Listener: [Listeners](../examples/210-Evt-EventListeners.cpp)
- Configuration: [Provide your own output streams](../examples/231-Cfg-OutputStreams.cpp)
- Generators: [Create your own generator](../examples/300-Gen-OwnGenerator.cpp)
- Generators: [Use map to convert types in GENERATE expression](../examples/301-Gen-MapTypeConversion.cpp)
- Generators: [Use variables in generator expressions](../examples/310-Gen-VariablesInGenerators.cpp)


@@ -0,0 +1,54 @@
// 301-Gen-MapTypeConversion.cpp
// Shows how to use map to modify generator's return type.

// TODO

#include <catch2/catch.hpp>

#include <string>
#include <sstream>

// Returns a line from a stream. You could have it e.g. read lines from
// a file, but to avoid problems with paths in examples, we will use
// a fixed stringstream.
class LineGenerator : public Catch::Generators::IGenerator<std::string> {
std::string m_line;
std::stringstream m_stream;
public:
LineGenerator() {
m_stream.str("1\n2\n3\n4\n");
if (!next()) {
throw Catch::GeneratorException("Couldn't read a single line");
}
}

std::string const& get() const override {
return m_line;
}

bool next() override {
return !!std::getline(m_stream, m_line);
}
};

// This helper function provides a nicer UX when instantiating the generator
// Notice that it returns an instance of GeneratorWrapper<std::string>, which
// is a value-wrapper around std::unique_ptr<IGenerator<std::string>>.
Catch::Generators::GeneratorWrapper<std::string> lines(std::string /* ignored for example */) {
return Catch::Generators::GeneratorWrapper<std::string>(
std::unique_ptr<Catch::Generators::IGenerator<std::string>>(
new LineGenerator()
)
);
}



TEST_CASE("filter can convert types inside the generator expression", "[example][generator]") {
auto num = GENERATE(map<int>([](std::string const& line) { return std::stoi(line); },
lines("fake-file")));

REQUIRE(num > 0);
}

// Compiling and running this file will result in 4 successful assertions
@@ -45,6 +45,7 @@ set( SOURCES_IDIOMATIC_TESTS
120-Bdd-ScenarioGivenWhenThen.cpp
210-Evt-EventListeners.cpp
300-Gen-OwnGenerator.cpp
301-Gen-MapTypeConversion.cpp
310-Gen-VariablesInGenerators.cpp
)

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