I'm having a problem hiding and showing an element depending of a boolean variable in Angular 2.
this is the code for the div to show and hide:
<div *ngIf="edited==true" class="alert alert-success alert-dismissible fade in" role="alert">
<strong>List Saved!</strong> Your changes has been saved.
</div>
the variable is "edited" and it's stored in my component:
export class AppComponent implements OnInit{
(...)
public edited = false;
(...)
saveTodos(): void {
//show box msg
this.edited = true;
//wait 3 Seconds and hide
setTimeout(function() {
this.edited = false;
console.log(this.edited);
}, 3000);
}
}
The element is hidden, when saveTodos function starts, the element is shown, but after 3 seconds, even if the variable come back to be false, the element does not hide. Why?
There are two options depending what you want to achieve :
You can use the hidden directive to show or hide an element
<div [hidden]="!edited" class="alert alert-success box-msg" role="alert">
<strong>List Saved!</strong> Your changes has been saved.
</div>
You can use the ngIf control directive to add or remove the element. This is different of the hidden directive because it does not show / hide the element, but it add / remove from the DOM. You can loose unsaved data of the element. It can be the better choice for an edit component that is cancelled.
<div *ngIf="edited" class="alert alert-success box-msg" role="alert">
<strong>List Saved!</strong> Your changes has been saved.
</div>
For you problem of change after 3 seconds, it can be due to incompatibility with setTimeout. Did you include angular2-polyfills.js library in your page ?
You should use the *ngIf Directive
<div *ngIf="edited" class="alert alert-success box-msg" role="alert">
<strong>List Saved!</strong> Your changes has been saved.
</div>
export class AppComponent implements OnInit{
(...)
public edited = false;
(...)
saveTodos(): void {
//show box msg
this.edited = true;
//wait 3 Seconds and hide
setTimeout(function() {
this.edited = false;
console.log(this.edited);
}.bind(this), 3000);
}
}
Update: you are missing the reference to the outer scope when you are inside the Timeout callback.
so add the .bind(this) like I added Above
Q : edited is a global variable. What would be your approach within a *ngFor-loop? – Blauhirn
A : I would add edit as a property to the object I am iterating over.
<div *ngFor="let obj of listOfObjects" *ngIf="obj.edited" class="alert alert-success box-msg" role="alert">
<strong>List Saved!</strong> Your changes has been saved.
</div>
export class AppComponent implements OnInit{
public listOfObjects = [
{
name : 'obj - 1',
edit : false
},
{
name : 'obj - 2',
edit : false
},
{
name : 'obj - 2',
edit : false
}
];
saveTodos(): void {
//show box msg
this.edited = true;
//wait 3 Seconds and hide
setTimeout(function() {
this.edited = false;
console.log(this.edited);
}.bind(this), 3000);
}
}
When you don't care about removing the Html Dom-Element, use *ngIf.
Otherwise, use this:
<div [style.visibility]="(numberOfUnreadAlerts == 0) ? 'hidden' : 'visible' ">
COUNTER: {{numberOfUnreadAlerts}}
</div>