How to implement parent-child component communication in Angular2
This article mainly introduces examples of the Angular2 parent-child component communication method. Now I share it with you and give it as a reference.
Angular2 official documentation has a detailed introduction to component interaction-->Documentation--Interaction between components. According to the document, there are 4 ways to interact between components, including:
Transfer data from parent component to child component through input binding (@Input decoration); child component Expose an EventEmitter property (@Output decoration), and use this property to emit events to the parent component when an event occurs.
Parent components and child components interact through local variables. (# var)
The parent component calls @ViewChild.
Parent components and child components communicate through services.
Here I will only summarize and introduce in detail three methods that I have used in the project. After reading this article, you can probably achieve the following results:
Create a project with the following project structure:
Communication between parent and child components through @Input and @Output decorators
@Input: This property binding is used by the parent component to pass data to the child component. Subcomponents can intercept property changes through the following two methods:
Use an input property setter to intercept value changes in the parent component.
Use ngOnchanges() to intercept changes in input attribute values.
@Output: This data binding is used by child components to pass data and events to parent components.
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The effect is as follows: (1. Parent component input, sub-component can output synchronously; 2. Sub-component input requires (3.) Click the button to trigger the launch event and transmit the data to the parent component.)
@Input: While the parent component is inputting, the child component can simultaneously obtain data for display. The core code is as follows:
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Use the setter to intercept changes in input attribute values, and declare a private variable in the child component to obtain the data passed by the parent component, thus shielding the upper layer from obtaining the lower layer information. (A simple point is not to let the parent component know what the child component uses to receive the passed data) The same effect can be obtained through this method.
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@Output: When the parent component receives data from the child component, the child component exposes an EventEmitter property. When an event occurs, the child component uses this property to emit (upward ejection) events. The parent component binds to this event property and responds when the event occurs. The core code is as follows:
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The parent component obtains the data of the child component by calling @ViewChild()
If the class of the parent component needs to read the properties and properties of the child component When you add a value or call a method of a subcomponent, you can inject the subcomponent into the parent component as ViewChild. ViewChild, as its name implies, allows you to see the properties and methods in subcomponents.
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The effect is as follows:
Core code of parent component:
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Parent component and child component communicate through services
The parent component and its child components share the same service and use this service to achieve two-way communication within the family.
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The effect is as follows:
The core code of the parent and child components is similar. In the constructor, the service instance is injected into itself. The parent and child components have a unique id. Whether the parent component or the child component calls the push() method to push data, both parties can receive the data. At this time, it is necessary to determine whether the parent component or the child component uses the data based on the ID. The core code is as follows:
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What I wrote above is not very complete, that is, before the end of the life cycle, that is, during the onDestroy cycle, the subscription must be cancelled.
The above is a summary of the component interactions that have been used recently. Personally, I feel that interaction through services is more scalable. For example, our project uses a dynamically displayed sidebar. Clicking to display the sidebar at different times will display different things. At this time, the sidebar is used as the parent component, and the child component is passed to the parent component as part of the message. The parent component dynamically generates a template based on the name of the child component and displays it on the sidebar. After talking so much nonsense, the following picture probably means:
The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
Related articles:
PHP closures and anonymous functions (detailed tutorial)
How to use the three-level linkage selector in the WeChat applet
How to use jquery to achieve the accordion effect
The above is the detailed content of How to implement parent-child component communication in Angular2. For more information, please follow other related articles on the PHP Chinese website!

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