Retrieving an individual instance of a component

Question

Retrieving an individual instance of a component

Is there a way to access a specific instance of a component within an app that uses it multiple times in other components? Currently, when I use the query command "fixture.debugElement.query(By.directive(ComponentName)).componentInstance;", it only recognizes the first instance of ComponentName.

Here is a simplified version of the example:

random.test.component.html

<random-test-child>
</random-test-child>

<snack-time
    [bestSnack]="cheeseAndCrackers">
</snack-time>

random.test.component.child.html

<snack-time
    [bestSnack]="applesAndOranges">
</snack-time>

<snack-time
    [bestSnack]="cookies">
</snack-time>

*all variable names are strings in their respective .ts files (e.g., applesAndOranges is "Apples and Oranges")

Currently, the query command selects the SnackTime component with the value "Apples and Oranges" as bestSnack. How can I specifically access the instances with "Cookies" or "Cheese and Crackers" without adding an id tag?

EDIT

Considering a different approach: In the spec file, I'm using fixture.debugElement.query(By.directive(SnackTime)).componentInstance to identify the SnackTime elements. I have now included another SnackTime in random.test.component.html:

<snack-time
    [bestSnack]="cheeseAndCrackers">
</snack-time>

<snack-time
    [bestSnack]="chipsAndSoda">
</snack-time>

I am thinking of creating a QueryList or array of the SnackTime elements and then selecting the specific instance from there. However, when I attempt this:

let componentsInThePage:SnackTime[] = fixture.debugElement.query(By.directive(SnackTime)).componentInstance;

I only get an array containing the first created SnackTime component, missing out on the other instances from random.test.component.html file (the ones in child.html are also not included). What would be the correct way to create a list/array of all SnackTime components?

angular typescript unit-testing karma-runner

Answer 1

Answer №1

If you are looking to access a component instance from your model.ts file, you could utilize a template reference variable.

To achieve this, you can use the @ViewChild decorator in the following manner:

@ViewChild('cookies') cookies: SnackTimeComponent

This allows you to capture a reference to the component instance.

Alternatively, you can directly interact with it within the template itself.

<div>I have {{cookies.numCookies}} cookies!</div>

(assuming that the numCookies property is present in the SnackTimeComponent class)

Answer 2

If you are looking to access a component instance from your model.ts file, you could utilize a template reference variable.

To achieve this, you can use the @ViewChild decorator in the following manner:

@ViewChild('cookies') cookies: SnackTimeComponent

This allows you to capture a reference to the component instance.

Alternatively, you can directly interact with it within the template itself.

<div>I have {{cookies.numCookies}} cookies!</div>

(assuming that the numCookies property is present in the SnackTimeComponent class)

Answer 3

Answer №2

Here is a solution to my recent edit.

To retrieve all instances of SnackTime elements, it is important to utilize "queryAll" instead of "query". By doing so, DebugElements can be converted into instances of SnackTime, resulting in an array that includes all SnackTime elements, even those found in other HTML files.

    let debugComponentsInThePage:DebugElement[] = fixture.debugElement.queryAll(By.directive(SnackTime));
    let componentsInThePage:SnackTime[] = [];

    for(var i=0; i<debugComponentsInThePage.length; i++){
        componentsInThePage[i] = debugComponentsInThePage[i].componentInstance;
        console.log(componentsInThePage[i]);
    }

Answer 4

Here is a solution to my recent edit.

To retrieve all instances of SnackTime elements, it is important to utilize "queryAll" instead of "query". By doing so, DebugElements can be converted into instances of SnackTime, resulting in an array that includes all SnackTime elements, even those found in other HTML files.

    let debugComponentsInThePage:DebugElement[] = fixture.debugElement.queryAll(By.directive(SnackTime));
    let componentsInThePage:SnackTime[] = [];

    for(var i=0; i<debugComponentsInThePage.length; i++){
        componentsInThePage[i] = debugComponentsInThePage[i].componentInstance;
        console.log(componentsInThePage[i]);
    }

Retrieving an individual instance of a component

Answer №1

Answer №2

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