A custom directive applied to both components(1/2)-in-spotlight is not working properly when using *ngIf. The issue resolves when I remove the *ngIf and one of the components that would not show in the current situation/"mode".
In the HTML file using the component (original):
<div>
<div>
<div>
<div>
<component1-in-spotlight *ngIf="mode===OptionOne"></component1-in-spotlight>
<component2-in-spotlight *ngIf="mode===OptionTwo"></component2-in-spotlight>
</div>
</div>
</div>
</div>
I found 2 solutions but both aren't effective or proper.
Duplicating the surrounding parent/grandparent components (placing the second case in an <ng-template #elseBlock>) and applying ngIf-else to the top most component (in the oversimplified example, a div) works. But, I'd have a lot of duplicate code and is a terrible solution.
Option 1 (to illustrate since it might be a bit confusing for some). In the HTML file using the component:
<div *ngIf="mode===OptionOne"; else myElseBlock">
<div>
<div>
<div>
<component1-in-spotlight></component1-in-spotlight>
</div>
</div>
</div>
</div>
</ng-template #myElseBlock>
<div>
<div>
<div>
<div>
<component2-in-spotlight></component2-in-spotlight>
</div>
</div>
</div>
</div>
</ng-template>
Using [hidden] on the 2 components instead of *ngIf seems fine. But there is never a case where the hidden component will be toggled to visible, it's decided upon creation and stays using either of the 2 components until it's destroyed. So, it should just only have one of the 2 components in DOM. Not just hiding it. Plus, that means flipping the logic--[hidden]="mode!==OptionOne". For now, it's just 2 options and seems unlikely more would be added, but I can't guarantee that.
--
It may seem like these 2 components are the same, so why not just have 1 component and pass in the mode and let the logic decide within the TS file of that component? Well, they both have different services that are injected into the constructor for the component. I was trying that before finding out and remembering that I can't use this before calling super() to decide which service to send up to the base class the component is extending.
Merging the 2 components and using #Input to get the "mode":
In the HTML file using the component:
<div>
<div>
<div>
<div>
<component-in-spotlight-merged [inputMode]="mode"></component-in-spotlight-merged>
</div>
</div>
</div>
</div>
In the component-in-spotlight-merged TS file--what I tried to do:
export class ComponentInSpotlightMergedComponent extends MyComponentBaseComponent {
#Input() inputMode: MyEnumType;
//...
constructor(
myService1: MyService1,
myService2: MyService2,
){
if(this.inputMode === Option1){
super(myService1);
}
else{
super(myService2);
}
}
//...
}
Using [hidden] can be for a quick fix, but is there a proper way to fix this?
Edit:
Not working meaning: It's a custom directive for tabbing focus between elements and the hotkey logic is binded here. Somehow the hotkey works but the focus is not working as it expected and none of my console.log() are outputted.
Angular 9+
You can use Angular NgSwitch directive as shown below.
<div [ngSwitch]="mode">
<!-- the same view can be shown in more than one case -->
<component1-in-spotlight *ngSwitchCase="option1">...</component1-in-spotlight>
<component2-in-spotlight *ngSwitchCase="option2">...</component2-in-spotlight>
<!--default case when there are no matches -->
<some-element *ngSwitchDefault>...</some-element>
</div>
The fix was to use setTimeout(() => myCallbackFn(), 0); (on my hotkey bind function that is called in ngAfterViewInit in a component class down the line--a view grandchild?).
I was in a rabbit hole of reading other stackoverflow questions and found How do I combine a template reference variable with ngIf? where a comment mentioned that ngIf takes a tick of time to evaluate. I eventually searched and found How to check whether ngIf has taken effect.
So I'm making a simple component library, and one item I am wanting to make is a simple grid that can take an array of components as input and place them into a grid with standardized styling. However, the tricky part is that I do not know what the input component will be. Is there a way to make the template dynamic to account for the fact that I will not know what the components selector will be?
i.e.
ts file would have
#Input() gridItems: any[]
and the template would be something like
<div *ngFor="let gridItem of gridItems">
<grid-item-selector></grid-item-selector>
</div>
is there a way to accomplish this?
I have a blazor component which binds to a collection of objects to render a list of cards. This works great as it is.
What I would like to enable is to declaratively define the list of cards as razor syntax. Something like the following:
<MyListComponent>
<Card>1st Card - Card-specific contents here</Card>
<Card>2nd Card - Card-specific contents here</Card>
<Card>3rd Card - Card-specific contents here</Card>
</MyListComponent>
Can this be achieved?
Note that i have created a datagrid/listview component which use RenderFragment "templates" for the Columns and Rows. But seems like this is different from what i am trying to achieve here.
Good morning everyone !
So have to create an application that displays many tables that all look the same (except their columns of course and the objects inside).
I have a master table component which can be summarized by:
<master-table>
<!-- here I define the master table style, pagination, etc etc
which is the same everywhere -->
</master-table>
In the master table component TS file I have basically options that are relevant for every page where this kind of table should be displayed, such as filterDate, clearSelection etc etc etc nothing very special.
The point is, I don't want to repeat this code every where because it is not necessary, so my idea was to create several component that would extend the master table component.
It works fine for the typescript values, but I am stuck with the HTML.
In my master table HTML I would like at some point some kind of placeholder something like this:
<master-table>
<standard-for-all-table></standard-for-all-table>
<!-- insert here child columns -->
</master-table>
In the components that extends my master table I was imagining then something like:
<!-- child component -->
<master-table></master-table>
<child-column>column definition</child-column>
Doing this would allow me to define only the columns in the child components HTML and they would be added automatically to the parent HTML at runtime...
Any idea how to do this ?
Cheers and thanks !
Basically you have to create your main master-table component and your generic list chid-column component and insert it in your parent html template structure.
I've edit the final part hope in a better understanding way...
Then you can structure your child component to contain all the properties you need and thanks to *ngIf show only the properties you return from your provider methods i.e. getClients(), getUsers(), getHouses(), also thanks to the #Input decorator you can inject this data directly from the parent to the child and create many components you want with just a change of the data.
So in your parent you can have something like
import { Component } from '#angular/core';
import { MY_DATA_FROMP_ROVIDER } from './mydata/provider';
#Component({
selector: 'master-table',
template: `
<ul>
<child-column *ngFor="let item of items"
[item]="item">
</app-hero-child>
</ul>
`
})
export class MasterTableComponent {
items:any
constructor(public data: MYDATAFROMPROVIDER) {
this.items = MYDATAFROMPROVIDER.myGetMethod();
}
And in your child
import { Component, Input } from '#angular/core';
import { INTERFACE } from './mydata/interface';
#Component({
selector: 'child-column',
template: `
<div *ngIf="item.id">{{item.id}}</div>
<div *ngIf="item.name">{{item.name}}</div>
<div *ngIf="item.address">{{item.address}}</div>
<div *ngIf="item.phone">{{item.phone}}</div>
`
})
export class ChildColumnComponent {
#Input() item: INTERFACE;
}
If you want to go deeper: Component Interaction
This guide is from official angular page Here
Here is the live sample of it
Not sure if these links could help.
But I actually worked on a project where we want to dynamically loading Child component into a Grid(Parent component).
And later on we can pass any component with different view inside the Grid
Guess that pretty close to your goal.
I have a problem with the new ng-content transclusion.
Let's say I have a component my-component that, in its ngOnInit() function does some heavy operation on load (for now, just a console.log()).
I have a wrapper, that displays the content via transclusion (my-wrapper.component.html).
<ng-content></ng-content>
If I set the surroundings up like this, the log statement doesn't show:
<my-wrapper *ngIf="false">
<my-component></my-component>
</my-wrapper>
I assume, the my-wrapper component does not get built, so the content is ignored.
But if I try to move the logic into the my-wrapper component like this (my-wrapper.component.html):
<ng-container *ngIf="false">
<ng-content></ng-content>
</ng-container>
I always see the console.log() output. I guess, the my-component gets built and then stored away until the *ngIf becomes true inside my-wrapper.
The intention was to build a generic "list-item + detail" component. Say I have a list of N overview-elements (my-wrapper), that get rendered in a *ngFor loop. Every of those elements has its own detail component (my-component) that is supposed to load its own data, once I decide to show more infos to a specific item.
overview.html:
<ng-container *ngFor="let item of items">
<my-wrapper>
<my-component id="item.id"></my-component>
</my-wrapper>
</ng-container>
my-wrapper.component.html:
<div (click)="toggleDetail()">Click for more</div>
<div *ngIf="showDetail">
<ng-content></ng-content>
</div>
Is there a way to tell Angular, to ignore the transcluded content until it is necessary to be added to the page? Analogously to how it was in AngularJS.
Based on the comment of #nsinreal I found an answer. I find it to be a bit abstruse, so I'm trying to post it here:
The answer is to work with ng-template and *ngTemplateOutlet.
In the my-wrapper component, set up the template like this (my-wrapper.component.html):
<div (click)="toggleDetail()">Click for more</div>
<div *ngIf="showDetail" [hidden]="!isInitialized">
<ng-container *ngTemplateOutlet="detailRef"></ng-container>
</div>
Note, that the [hidden] there is not really necessary, it hides the "raw" template of the child until it decides it is done loading. Just make sure, not to put it in a *ngIf, otherwise the *ngTemplateOutlet will never get triggered, leading to nothing happening at all.
To set the detailRef, put this in the component code (my-wrapper.component.ts):
import {Â ContentChild, TemplateRef } from '#angular/core';
#Component({ ... })
export class MyWrapperComponent {
#ContentChild(TemplateRef) detailRef;
...
}
Now, you can use the wrapper like this:
<my-wrapper>
<ng-template>
<my-component></my-component>
</ng-template>
</my-wrapper>
I am not sure, why it needs such complicated "workarounds", when it used to be so easy to do this in AngularJS.
By doing this:
<my-wrapper *ngIf="false">
<my-component></my-component>
</my-wrapper>
You are not calling MyComponent component, because the *ngIf is false. that means, that not calling it you are not instancing it and, therefore, not passing through its ngOnInit. And that's why you are not getting the console log.
By doing this:
<ng-container *ngIf="false">
<ng-content></ng-content>
</ng-container>
You are inside the component, you are just limiting what to render in your template, but you already instanced your component and, therefore, you passed through your ngOnInit and you get your console log done.
If, you want to limit something (component call with selector or a ng-content or even a div) until you have some data available, you can do the following:
datasLoaded: Promise<boolean>;
this.getData().subscribe(
(data) => {
this.datasLoaded = Promise.resolve(true); // Setting the Promise as resolved after I have the needed data
}
);
And in your template:
<ng-container *ngIf="datasLoaded | async">
// stuff here
</ng-container>
Or:
<my-component *ngIf="datasLoaded | async">
// Didn't test this one, but should follow the same logic. If it doesn't, wrap it and add the ngIf to the wrapper
</my-component>
It’s because Ng content happens at the build time and when you pass the content it is actually not removed or recreated with the ngIf directive. It is only moved and the component is instantiated .
I encountered this problem recently as well but settled on a different solution than the currently accepted one.
Solution (TL;DR)
(Solution is for AngularDart; I figure it's similar in Angular though)
Use a structural directive; tutorials linked below.
Instead of:
<my-wrapper>
<my-contents></my-contents>
</my-wrapper>
your usage becomes:
<div *myWrapper>
<my-contents></my-contents>
</div>
which is shorthand for the following (in AngularDart; I think Angular uses <ng-template>)
<template myWrapper>
<div>
<my-contents></my-contents>
</div>
</template>
The MyWrapper directive logic is similar to NgIf except it has its own logic to compute the condition. Both of the following tutorials explain how to create an NgIf-like directive and how to pass it your own inputs using the special microsyntax (e.g. *myWrapper="myInput: expression"). Note that the microsyntax doesn't support outputs (#Output), but you can mimic an output by using an input that is a function.
Tutorial for Angular
Tutorial for AngularDart
Caveat: Since this is just a directive, it shouldn't do anything more complicated than instantiating a template ref at the appropriate time and maybe specifying some DI providers. For example, I would avoid trying to apply styles or instantiating a complex tree of components in the directive. If I wanted to create a list component, I would probably take the #ContentChild(TemplateRef) approach described in another answer; you would lose the asterisk shorthand for creating <template> but you would gain the full power of components.
My problem
My team owns an app that's part of a larger web application with other apps owned by other teams. Our components assume they can inject a MyAppConfiguration object, but this object can only be injected after it is loaded with an asynchronous request. In our app this is not a problem: we have a "shell" component that hides everything behind an ngIf until the configuration is loaded.
The problem is when other teams want to reference our components. We don't want them to duplicate the "wait until configuration is loaded" logic every time, so I tried creating a wrapper component that can be used like so:
<my-app-wrapper>
<my-app-component></my-app-component>
</my-app-wrapper>
The wrapper injects a service object and hides its contents behind an ngIf until the service says that the configuration is loaded.
Like the question poster, I discovered that the ng-content approach doesn't work as intended: while the contents are correctly hidden from the DOM, Angular still instantiates the components causing dependency injection to fail.
The solution that I settled on was to rewrite the wrapper component as a structural directive.