Call ngoninit from another component

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Call ngoninit from another component

We will execute a function in a component from another component in Angular. We will pass the data from one component to another component as well. In this post, we will execute a function in a component from another component in A ngular. For this, w e are using EventEmitter service. In A ngular, a component can emit an event using Output and EventEmitter.

The eventEmitter. We can use various options to execute functions from another component in a ngular.

call ngoninit from another component

In Angular 7, we can create a routing module along with the project creation. It will take some moments to create all the node modules.

Our project will be created after some time. We can create three components. We can open the code in any IDE and edit the code.

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I am using Visual Studio Code for editing the code. This will automatically invoke the event in service. View All. Sarathlal Saseendran Updated date, Dec 22 We will also create a function to invoke the EventEmitter method in service. Our code is ready now. We can run the application. We can click the first component link. It will call the function in the first component.

It will execute the function from the first component and will show the same message box as given below. We can run the application again and click first component and then click second component. We have successfully passed data from one component to another component and called the function. In this post, we have created an event emitter service and executed a function in a component from another component. We have passed the data from one component to another component too.

Next Recommended Article.What if, instead of common data functionality, you want common UI functionality? For example, consider a simple scenario where you want to navigate from one component to another using buttons.

A simple way to implement this is to create a button, call a method in the code which then uses the Angular router to navigate to the page. Typescript and Angular gives you a pretty easy way to handle this encapsulation; welcome to the world of inherited components.

If you're interested in learning Angular in a comprehensive and structured way, I highly recommend you check out ng-book. Learning from an organized and up-to-date resource like that should speed up your learning quite a bit.

Plus, this is an affiliate linkso if you purchase the course you help Alligator. We're passing some flag to the ng new command to add routing to our app and not to add any testing files. The --m flag here specifies the module to which the component should belong to. Take note of the accessibility level. Next, add a method to the base component called openPage which takes a string and uses it to navigate to a route note: use the tick below instead of the single quote for a template literal :.

Open app-routing. As well as adding the router and injecting it into the BaseComponent constructor using super :. Due to the inheritance passed from the base component, anything defined on the base component is available to all components which extend it.

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If you think about how you would do a similar inheritance in a language like Cyou would call something such as base. TypeScript turns the code into JavaScript and the base component module is imported into the pageone component so it can be used directly by the component. This is also why we need to keep our injected modules public rather than private. In TypeScript, super is how the constructor of the base component is called and requires all the injected modules to be passed.

When modules are private, they become separate declarations. Keep them public and pass them using superand they remain a single declaration. Whether you are handling navigation, common modal alert UI or anything else, using the inheritance model granted via TypeScript to extend components is a powerful tool to keep in our toolbox.

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Tweet It.All modern frameworks are designed to help implement UI composition with components. Naturally you will have a parent-child hierarchy and the framework should provide a way to communicate between the child and parent.

I prefer using the first method for the stateless presentational components while I employ DI for the stateful container components. This article is concerned with the first method. Particularly it explores the underlying mechanism of how Angular updates child input propertie s when parent bound values change. It continues a series of articles on change detection and builds upon my previous article The mechanics of DOM updates in Angular. Since we will be looking how Angular updates input properties for both DOM elements and components it is assumed that you know how Angular represents directives and components internally.

As you probably know Angular provides template syntax for property bindings — []. This syntax is generic so it can be applied for both child components and native DOM elements. Now, whenever the AText property changes on the A component Angular will automatically update the property textContent on B component and span.

It will also call ngOnChanges lifecycle hook for the child component. You may be wondering how Angular knows that BComponent and span support textContent binding. For the components and directives it checks the metadata attached to the class and ensures that bound property is listed in the input decorator property.

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If the bound property not found the compiler throws an error:. This is a well document functionality and there should be no problem with its understanding. The third is an element definition for the span.

call ngoninit from another component

One thing that distinguishes this factory from other you may have seen is the parameters that these node definitions take. This parameter is called props as you may see from the directiveDef function parameters list :. It is an object with keys where each key defines a bindings index and the property name to update. For our example there will be only one binding for the textContent property:. When Angular creates a directive definition node it uses these values to generate binding for the view node.

3 Ways to Pass Async Data to Angular 2+ Child Components

During change detection each binding determines the type of operation Angular should use to update the node and provides context information. The binding type is set using bindings flags. In case of property update for each binding the compiler sets the following flags:. And since we also have bindings on the span element, the compiler generates the props parameter supplied to the span element definition as well:. For elements this parameter has a bit different structure — an array of props.

The span has only one input binding so there is only one child array. The first number in the array specifies the type of operation to be used with the binding — which is property update:. The other possible variants are the following and they are explained in The mechanics of DOM updates in Angular :. You should be familiar with the second updateRenderer function already from the article about DOM update.

Angular Component Inheritance

The first function is called updateDirectives. These both functions are defined by the ViewUpdateFn interface and both are attached to the view definition:. So why two functions? And these operations are performed at different stages during change detection cycle.

So Angular has two functions each specializing on a particular node definition and calls them at different stages when checking a component:.You can also check out this article for how to add routing to a CRM application by example. The Angular router is an essential element of the Angular platform. It allows developers to build Single Page Applications with multiple states and views using routes and components and allows client side navigation and routing between the various components.

You can use the browser's URL to navigate between Angular components in the same way you can use the usual server side navigation. Angular 9 provides a powerful router that allows you to map browser routes to components.

So let's see how we can add routing to applications built using Angular 9. Angular applications are built as a hierarchy of components or a tree of components that communicate with each other using inputs and outputs. A Component decorator marks a class as an Angular component and provides configuration metadata that determines how the component should be processed, instantiated, and used at runtime.

In component-based applications such as Angular applications, a screen view is implemented using one or more components. Routing in Angular is also refereed to as component routing because the Router maps a single or a hierarchy of components to a specific URL. In Angular, a route is an object instance of Route that provides information about which component maps to a specific path.

A path is the fragment of a URL that determines where exactly is located the resource or page you want to access. You can get the path by taking off the domain name from the URL. In Angular you can define a route using route configurations or instances of the Route interface. A collection of routes defines the router configuration which is an instance of Routes.

These are the commonly used properties of routes but there are many others. You can find the rest of properties from the official docs. The Angular router has a powerful matching algorithm with various built-in and custom matching strategies. The builtin matching strategies are prefix the default and full.

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This is not always the wanted behavior. In some scenarios, you want the router to match the full path before rendering a component. You can set the full strategy using the pathMatch property of a route. For example:. A special case of using the full property is when you want to match the empty path. Because using the prefix strategy will match all paths since the empty path prefixes all paths.RxJS Masterclass is here. Want to level up your Angular skills?

Who doesn't. Here's what you need to know. Called once, after the first ngOnChanges. First impressions are interesting because, going by the name alone, you would expect the OnInit hook to be executed first when the component is mounted.

That almost is the case, but our friend OnChanges actually runs just before OnInit! You may be asking yourself; what are some good use cases for OnInit? Should class property assignments happen here or can they just happen at variable declaration? In this article, we will review how to implement OnInitcommon use cases for OnInitand wrap-up with some bonus use cases for OnInit to answer all those questions. OnInit is an Angular lifecycle method, that can be hooked into components and directives in Angular.

By defining a specific method named ngOnInit on our class, we are telling the Angular runtime, that it should call our method at the appropriate time.

This is a powerful and declarative way to add specific initialization logic near the beginning of our class lifecycle. As with other Angular lifecycle methods, adding the actual hook for OnInit is relatively simple. The first step to implementing OnInit is to add OnInit after the implements keyword on a component or directive. Now that we have added the OnInit after implements the TypeScript intellisense will underline the class declaration in red, giving a warning that ngOnInit was not found.

For a deep dive on Constructor vs OnInit checkout out our in-depth writeup here! Well the answer, in short, is that we should place our initialization logic in ngOnInit.

The constructor is best left up to the purpose of injecting dependencies, such as services, into our components. This means we can access anything passed down into the component inside the ngOnInit hook.

Implementing OnInit was a simple two-step process. We can make a call to this service, get back our list of repositories and render them to the browser.

GithubReposComponent will be responsible for subscribing to the results of GithubService. But, what is the best way to go about this? Finally, we have our detail page, GithubRepoDetailComponent component, for displaying repo details when navigated to.Let's start with a common use case.

You have some data you get from external source e. You want to display it on screen. However, instead of displaying it on the same component, you would like to pass the data to a child component to display.

For example, you have a blogger component that will display blogger details and her posts. Blogger component will gets the list of posts from API. Instead of writing the logic of displaying the posts in the blogger component, you want to reuse the posts component that is created by your teammate, what you need to do is pass it the posts data.

The posts component will then group the posts by category and display accordingly, like this:.

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It might look easy at the first glance. Most of the time we will initiate all the process during our component initialization time - during ngOnInit life cycle hook refer here for more details on component life cycle hook. In our case, you might think that we should run the post grouping logic during ngOnInit of the posts component. However, because the posts data is coming from server, when the blogger component passes the posts data to posts component, the posts component ngOnInit is already fired before the data get updated.

Your post grouping logic will not be fired. Then, we assign the data to posts property. Subsequently, we bind posts to posts component in our view template.

Please take note that, usually we will perform HTTP call in service. However, since it's not the focus of this tutorial to shorten the tutorialwe will do that it in the same component. We have an input called data which will receive the posts data from parent component. In our case, blogger component will provide that. You can see that we implement two interfaces OnInit and OnChanges.

These are the lifecycle hooks that Angular provide to us. We have not done anything in both ngOnInit and ngOnChanges just yet. The groupByCategory function is our core logic to group the posts by category. After the grouping, we will loop the result and display the grouped posts in our template. Remember to import these components in you module e. Save and run it. You will see a pretty empty page with the blogger name only. That's because we have not code our solution yet.

Solution one is the easiest. We will bind the post component only if the posts variable has a value. Then, we are safe to run our grouping logic in posts component ngOnInit. That means it's guaranteed that everytime data input value changed, our grouping logic will be triggered if we put our code here.

Please notes that changes is a key value pair object. The key is the name of the input property, in our case it's data. Whenever writing code in ngOnChangesyou may want to make sure that the logic run only when the target data changed, because you might have a few inputs. One thing I don't like about this solution is that we lose the strong typing and need to use magic string "data". In case we change the property name data to something else, we need to remember to change this as well.

We can utilize RxJs BehaviorSubject to detect the changes. I suggest you take a look at the unit test of the official document here before we continue.

Just assume that BehaviorSubject is like a property with get and set abilities, plus an extra feature; you can subscribe to it.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.

They are getting some Id from localstorage which was set by clicking on a link in another component. So, as it was set on click, initially when page loads first time before click, I am not able to get the ID and the subsequent functionality is not working. So, my question is can I call the onInit method of the app. Or is there any better approach to do this.

Please use the following link Javascript - telling setInterval to only fire x amount of times? You don't have to call the ngOnInit twice.

The variable childItem. You could try the following in the service. And also make sure the value obtained from session storage is used at the beginning of the app life-cycle.

Learn more. Call app component ngOnInit second time on click of a link Ask Question. Asked 3 days ago. Active 3 days ago.

call ngoninit from another component

Viewed 23 times. I am restructuring an angular project where I found below functionality. In app. Are you using this other component in the app component template? Active Oldest Votes. Here You can write contents of your oninit using setintervalX This way you can call contents of oninit multiple times. Shlok Nangia Shlok Nangia 2 2 silver badges 10 10 bronze badges.

Michael D Michael D 3, 1 1 gold badge 8 8 silver badges 23 23 bronze badges. In the code you've shown in the question, this.

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