如何教谷歌测试从 std 打印类型？

Question

我有一个需要打印出来的测试std::pair<std::string, std::string>，但即使我为该 googletest 声明并定义了一个运算符，它也会抱怨它找不到它。

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谷歌测试手册提到了这一点

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// It\'s important that the << operator is defined in the SAME\n// namespace that defines Bar.  C++\'s look-up rules rely on that.\n

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我应该重新打开std命名空间并将其放置operator<<(std::ostream& os, const std::pair<std::string, std::string>& p)在那里吗？

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代码摘录：

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// included from somewhere else in legacy code:\n// typedef ::std::map< ::std::string, ::std::string > AttrList;\nbool UserDefinedTypeMatcher::MatchAndExplain(UserDefinedType& r, testing::MatchResultListener* listener) const {\n  typedef AttrList::const_iterator AttrIt;\n  std::pair<AttrIt, AttrIt> pattr = std::mismatch(r.attr.begin(), r.attr.end(), expectedUserDefinedType.attr.begin());\n  if(pattr.first != r.attr.end() && pattr.second != expectedUserDefinedType.attr.end())\n  {\n    *listener << "\\nFail: attr members differ on the following elements: "\n        << "from given UserDefinedType: " << *pattr.first << \'\\n\'\n        << ", from expected UserDefinedType : " << *pattr.second << \'\\n\';\n    return false;\n  }\n\n  return true;\n}\n

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编译器错误：

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/opt/gmock-1.7.0/include/gmock/gmock-matchers.h: In member function \xe2\x80\x98testing::MatchResultListener& testing::MatchResultListener::operator<<(const T&) [with T = std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >]\xe2\x80\x99:\ntest/src/matchers/UserDefinedTypeMatchers.cpp:50:   instantiated from here\n/opt/gmock-1.7.0/include/gmock/gmock-matchers.h:93: error: no match for \xe2\x80\x98operator<<\xe2\x80\x99 in \xe2\x80\x98*(std::ostream*)((testing::MatchResultListener*)this)->testing::MatchResultListener::stream_ << x\xe2\x80\x99\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:108: note: candidates are: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>& (*)(std::basic_ostream<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:117: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ios<_CharT, _Traits>& (*)(std::basic_ios<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:127: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:165: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:169: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:173: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ostream.tcc:91: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:180: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ostream.tcc:105: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:191: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:200: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:204: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:209: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:213: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:221: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:225: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char, _Traits = std::char_traits<char>]\n/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ostream.tcc:119: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_streambuf<_CharT, _Traits>*) [with _CharT = char, _Traits = std::char_traits<char>]\n/opt/gmock-1.7.0/gtest/include/gtest/gtest-message.h:232: note:                 std::ostream& testing::operator<<(std::ostream&, const testing::Message&)\n/opt/gmock-1.7.0/gtest/include/gtest/gtest-test-part.h:120: note:                 std::ostream& testing::operator<<(std::ostream&, const testing::TestPartResult&)\n

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编辑：

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好的，所以我了解到我可以执行以下操作：

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bool UserDefinedTypeMatcher::MatchAndExplain(UserDefinedType& r, testing::MatchResultListener* listener) const {\n    std::pair<std::string, std::string> mypair;\n    // use and manipulate mypair\n    *listener << ::testing::PrintToString(mypair);\n}\n

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