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Copy file name to clipboardExpand all lines: 10-templates-exceptions-lambdas-smart-pointers.md
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@@ -123,10 +123,10 @@ public:
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}
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};
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auto o1 = Opt{ 1.2 };
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auto o2 = Opt{ 3 };
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auto o3 = Opt{};
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auto o4 = Opt<size_t>{};
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auto o1 = Opt{ 1.2 }; // T = double, valid = true
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auto o2 = Opt{ 3 }; // T = int, valid = true
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auto o3 = Opt{}; // T = char, valid = false
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auto o4 = Opt<size_t>{}; // T = size_t, valid = false
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```
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Some things to note about this program:
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* Calling member function`hasValue()` is always safe, yielding a`bool`. Calling`get()` on an`Opt` with no value immediately terminates the program (the keyword`throw` is explained later in this Chapter).
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Of course, this simple class is of limited practical use, if you need a type to be considered optionally valid without using a "special" value to indicate this, thenmake use of`std::optional<T>` from the Standard Library.
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Of course, this simple class is of limited practical use; if you need a type to be considered optionally valid without using a "special" value to indicate this, thenmaking use of`std::optional<T>` from the Standard Library is recommended.
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Member functions can be template functions, too. The following program defines a`Stringy` class with a`std::string` member, which can be initialized from another`std::string`, a`std::string_view` or a`const char *`:
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cout << "Name not recognized!\n";
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}
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}
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}
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}
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```
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This is one of the larger programs we have seen, and covers much of the contents of this Chapter:
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* Change`Pupil` and`Class` to be`class`es instead of`struct`s, with`private:` data members. Hint: you will need to write some`public:` getters.