coco
62 lines
2.3 KiB
Markdown
62 lines
2.3 KiB
Markdown
# Implicit navigation
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<img src="https://i.imgur.com/hKvOs3w.gif" width="450">
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How can we go from one part of the tree to another? In almost all cases navigation can be implicit instead of explicit. We don't need to specify the target – navigation will happen as a consequence of individual pieces of the puzzle.
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!!! info "Relevant methods"
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- `ParentNode.onChildFinished(child: Node)` can be overridden by client code to handle a child finishing
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- `Node.finish()` invokes the above method on its parent
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## Use-case 1
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<img src="https://i.imgur.com/jkZQJBC.png" width="450">
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### Requirement
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After onboarding finishes, the user should land in the message list screen.
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### Solution
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1. `O3` calls its `finish()` method
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2. `Onboarding` notices `O3` finished; if it had more children, it could switch to another; now it calls `finish()` too
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3. `Logged in` notices `Onboarding` finished, and switches its navigation to `Main`
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4. `Main` is initialised, and loads its default navigation target (based on product requirements) to be `Messages`
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5. `Messages` is initialised, and loads its default navigation target to be `List`
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!!! success "Bonus"
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Every `Node` in the above sequence only needed to care about its own local concern.
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## Use-case 2
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<img src="https://i.imgur.com/jkZQJBC.png" width="450">
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### Requirement
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Pressing the logout button on the profile screen should land us back to the login screen.
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### Solution
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1. `Root` either implements a `logout` callback, or subscribes to the changes of a user repository; in both cases, either the callback or the repository is passed down the tree as a dependency
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2. `Profile` invokes the callback or a `logout` method on the repository
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3. `Root` notices the state change, and switches its navigation to the `Logged out` scope
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4. `Logged out` loads its initial navigation target, `Login`
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!!! success "Bonus"
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Note how the entire `Logged in` scope is destroyed without any extra effort. The next time a login happens, all state is created anew.
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## Summary
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Implicit navigation allows you to implement navigation without introducing unnecessary coupling in the tree, and successfully covers the majority of navigation scenarios.
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In case it's not enough to meet your needs, see the next chapter, [Explicit navigation](explicit-navigation.md)
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