STYLE: Replace (const std::string) casts with C++17 std::string_view

[N-Dekker]

Prevented potential static analysis warnings, like Clang-Tidy:

C-style casts are discouraged; use static_cast [google-readability-casting]

And JetBrains ReSharper:

C-style cast is used instead of a C++ cast

Note that std::string_view is more lightweight than std::string.

• Follow-up to pull request STYLE: Use ITK_TEST_EXPECT_EQUAL to compare class names in QEMesh #4583

[N-Dekker]

By the way, I noticed that GoogleTest has a few macro's specifically for string comparison, avoiding the need to manually convert the arguments to std::string or std::string_view. Might be worth considering 😃

[dzenanz]

GoogleTest has a few macro's specifically for string comparison

Make a competing PR using those? 😄

[N-Dekker]

/azp run ITK.macOS

[N-Dekker]

Note that std::string_view only provides read-only to the data, so in that sense, it's similar to const std::string &.

[N-Dekker]

Thanks for merging, @hjmjohnson! For the record, none of the recent versions of this test (pull request #4576, #4583, #4587) properly handle the possibility of deleteCenterVertex->GetNameOfClass() accidentally returning a null. I was hoping that the std::string_view(const char*) constructor would support a null char pointer as argument, but unfortunately it does not. Neither does the originally used std::string(const char*) constructor. It's undefined behavior 🤷

If you just want to ensure that this GetNameOfClass() override has code coverage, you might as well just checks that the returned pointer is not null. For example as follows:

ITK_TEST_EXPECT_TRUE(deleteCenterVertex->GetNameOfClass());

Instead of doing the string comparison check.

[dzenanz]

Is GetNameOfClass() ever expected to return a NULL pointer? So that problem might be moot.

[N-Dekker]

Is GetNameOfClass() ever expected to return a NULL pointer?

No, but unit tests allow us to express what we expect, and what we do not expect 😸

Obviously it's easy for anyone to write a malicious GetNameOfClass() override that does return NULL. 😸 😸