Which of the following scenarios would provide for an ideal use of the refs file system?
Refs provide a way to access DOM nodes or React elements created in the render method. Show
In the typical React dataflow, props are the only way that parent components interact with their children. To modify a child, you re-render it with new props. However, there are a few cases where you need to imperatively modify a child outside of the typical dataflow. The child to be modified could be an instance of a React component, or it could be a DOM element. For both of these cases, React provides an escape hatch. When to Use RefsThere are a few good use cases for refs:
Avoid using refs for anything that can be done declaratively. For example, instead of exposing Don’t Overuse RefsYour first inclination may be to use refs to “make things happen” in your app. If this is the case, take a moment and think more critically about where state should be owned in the component hierarchy. Often, it becomes clear that the proper place to “own” that state is at a higher level in the hierarchy. See the Lifting State Up guide for examples of this.
Creating RefsRefs are created using
Accessing RefsWhen a ref is passed to an element in
The value of the ref differs depending on the type of the node:
The examples below demonstrate the differences. Adding a Ref to a DOM ElementThis code uses a
React will assign the Adding a Ref to a Class ComponentIf we wanted to wrap the
Note that this only works if
Refs and Function ComponentsBy default, you may not use the
If you want to allow people to take a You can, however, use the
Exposing DOM Refs to Parent ComponentsIn rare cases, you might want to have access to a child’s DOM node from a parent component. This is generally not recommended because it breaks component encapsulation, but it can occasionally be useful for triggering focus or measuring the size or position of a child DOM node. While you could add a ref to the child component, this is not an ideal solution, as you would only get a component instance rather than a DOM node. Additionally, this wouldn’t work with function components. If you use React 16.3 or higher, we recommend to use ref forwarding for these cases. Ref forwarding lets components opt into exposing any child component’s ref as their own. You can find a detailed example of how to expose a child’s DOM node to a parent component in the ref forwarding documentation. If you use React 16.2 or lower, or if you need more flexibility than provided by ref forwarding, you can use this alternative approach and explicitly pass a ref as a differently named prop. When possible, we advise against exposing DOM nodes, but it can be a useful escape hatch. Note that this approach requires you to add some code to the child component. If you have absolutely no control over the child component implementation, your last option is to use
Callback RefsReact also supports another way to set refs called “callback refs”, which gives more fine-grain control over when refs are set and unset. Instead of passing a The example below implements a common pattern: using the
React will call the You can pass callback refs between components like you can with object refs that were created with
In the example above, Legacy API: String RefsIf you worked with React before, you might be familiar with an older API where the
Caveats with callback refsIf the What type of structure is usually used to organize folders in a file system?Hierarchical File Structure
All files in the UNIX file system are organized in a multi-leveled hierarchy called a directory tree. A family tree is an example of a hierarchical structure that represents how the UNIX file system is organized.
What specific powershell cmdlet shows information about NFS shares on a server?The Get-NfsSharePermission cmdlet gets information about access permissions granted by a Network File System (NFS) server that has an NFS share configured.
What utility is the preferred method for creating and managing shares within Server 2012 R2?Cards
Which is responsible for management of adding removing and renaming domains in a forest?Cards
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