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Merge pull request #628 from DavidDeprost/master

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Update ch17-03-oo-design-patterns.md
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Carol (Nichols || Goulding)
2017-04-16 13:24:34 -04:00
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second-edition/src/ch17-03-oo-design-patterns.md
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@@ -196,11 +196,11 @@ works as we intend.
Next up is requesting a review of a post, which should change its state from
`Draft` to `PendingReview`. We want `post` to have a public method named
`request_review` that will take a mutable reference to `self`. Then we're going
to call a `request_review` method on the state that we're holding, and that
`request_review` method will consume the current state and return a new state.
In order to be able to consume the old state, the state `request_review` method
needs to take ownership of the state value. This is where the `Option` comes
in: we're going to take the `Some` value out of the `state` field and leave a
to call an internal `request_review` method on the state that we're holding, and
this second `request_review` method will consume the current state and return a
new state. In order to be able to consume the old state, the second `request_review`
method needs to take ownership of the state value. This is where the `Option` comes
in: we're going to `take` the `Some` value out of the `state` field and leave a
`None` in its place since Rust doesn't let us have unpopulated fields in
structs. Then we'll set the post's `state` value to the result of this
operation. Listing 17-15 shows this code: