Fix optional.md documentation, add example.
The documentation was referring to the struct base::nullopt_t
where it should have been using the constexpr base:nullopt instead,
leading to confusing compiler errors when following the examples.
Also add an example showing how to pass an empty optional argument,
since this wasn't immediately obvious to me.
R=mlamouri
constexpr nullopt_t nullopt(0);
https: //cs.chromium.org/chromium/src/base/optional.h defines:
Change-Id: I4fc246ebd5282794e44d88587336f2190250350d
Reviewed-on: https://chromium-review.googlesource.com/662982
Reviewed-by: Mounir Lamouri <[email protected]>
Commit-Queue: Klaus Weidner <[email protected]>
Cr-Commit-Position: refs/heads/master@{#501682}diff --git a/docs/optional.md b/docs/optional.md
index 70c9efb..14b3ed8 100644
--- a/docs/optional.md
+++ b/docs/optional.md
@@ -22,13 +22,20 @@
When initialized without a value, `base::Optional<T>` will be empty. When empty,
the `operator bool` will return `false` and `value()` should not be called. An
-empty `base::Optional<T>` is equal to `base::nullopt_t`.
+empty `base::Optional<T>` is equal to `base::nullopt`.
```C++
base::Optional<int> opt;
opt == true; // false
opt.value(); // illegal, will DCHECK
-opt == base::nullopt_t; // true
+opt == base::nullopt; // true
+```
+
+To pass an empty optional argument to another function, use `base::nullopt`
+where you would otherwise have used a `nullptr`:
+
+``` C++
+OtherFunction(42, base::nullopt); // Supply an empty optional argument
```
To avoid calling `value()` when an `base::Optional<T>` is empty, instead of
@@ -49,7 +56,7 @@
All basic operators should be available on `base::Optional<T>`: it is possible
to compare a `base::Optional<T>` with another or with a `T` or
-`base::nullopt_t`.
+`base::nullopt`.
```C++
base::Optional<int> opt_1;
@@ -60,7 +67,7 @@
opt_1 <= opt_2; // true
opt_1 == 1; // true
-opt_1 == base::nullopt_t; // false
+opt_1 == base::nullopt; // false
```
`base::Optional<T>` has a helper function `base::make_optional<T&&>`:
