Template reference for direct access in Angular - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when accessing an input value via template reference?

Consider this Angular template snippet:

<input #userInput type="text" value="Hello">
<button (click)="logValue(userInput.value)">Log</button>

What will be logged when the button is clicked?

Angular

logValue(value: string) {
  console.log(value);
}

A An error because #userInput is not accessible in the component

B "Hello"

C undefined

D "userInput"

💡 Hint

Template reference variables allow direct access to DOM elements in the template.

The template reference #userInput points to the input element. Accessing userInput.value gets the current value, which is "Hello" initially.

📝 Syntax

intermediate

Which template reference syntax correctly accesses a child component's method?

Given a child component <app-child> with a method reset(), which template code correctly calls reset() from a button click?

A &lt;app-child #childComp&gt;&lt;/app-child&gt;<br>&lt;button (click)="childComp.reset()"&gt;Reset&lt;/button&gt;

B &lt;app-child #childComp&gt;&lt;/app-child&gt;<br>&lt;button (click)="childComp()"&gt;Reset&lt;/button&gt;

C &lt;app-child&gt;&lt;/app-child&gt;<br>&lt;button (click)="#childComp.reset()"&gt;Reset&lt;/button&gt;

D &lt;app-child #childComp&gt;&lt;/app-child&gt;<br>&lt;button (click)="reset()"&gt;Reset&lt;/button&gt;

💡 Hint

Template reference variables can be used to call public methods of child components.

Option A correctly assigns a template reference #childComp to the child component and calls its reset() method on button click.

🔧 Debug

advanced

Why does this template reference cause a runtime error?

Template snippet:

<app-input #inputRef></app-input>
<button (click)="inputRef.focus()">Focus</button>

Runtime error: "inputRef.focus is not a function". Why?

A The template reference variable is not accessible inside the (click) event.

B The input element does not have a focus() method in Angular templates.

C The template reference points to an Angular component, not a native input element, so focus() is undefined.

D The input element is missing a closing tag causing the reference to fail.

💡 Hint

Check what the template reference actually points to.

If the input is wrapped in a component, the template reference points to the component instance, which lacks native DOM methods like focus().

❓ state_output

advanced

What is the value of the template reference variable after user input?

Template:

<input #nameInput type="text">
<button (click)="showName(nameInput.value)">Show</button>

Component method:

showName(name: string) {
  this.displayName = name;
}

If the user types "Angular" in the input and clicks Show, what is the value of displayName?

A "" (empty string)

B "nameInput"

C undefined

D "Angular"

💡 Hint

Template reference variables reflect the current state of the DOM element.

The value property of the input element reflects the typed text. Passing nameInput.value sends "Angular" to the method.

🧠 Conceptual

expert

Why use template reference variables instead of @ViewChild for direct access?

Which reason best explains when template reference variables are preferred over @ViewChild in Angular?

A Template references allow direct access in the template without needing component class code, useful for simple DOM interactions.

B @ViewChild is deprecated and should not be used anymore.

C @ViewChild only works with native DOM elements, not Angular components.

D Template references can access private component properties, while @ViewChild cannot.

💡 Hint

Think about where and how you want to access elements or components.

Template references provide quick access in the template itself, avoiding extra code in the component class for simple tasks.

Practice

1. What is the main purpose of a #templateReference in Angular templates?

easy

A. To bind data between components

B. To define a new Angular component

C. To create a service for dependency injection

D. To directly access a DOM element or component instance in the template

Solution

1. Step 1: Understand what template references do

   Template references let you name elements or components in the template for direct access.

2. Step 2: Identify their use

   They are used to access DOM elements or component instances directly without extra code.

3. Final Answer:

   To directly access a DOM element or component instance in the template -> Option D

4. Quick Check:

   Template reference = direct element/component access [OK]

Hint: Template references name elements for direct access [OK]

Common Mistakes:

• Confusing template references with component declarations
• Thinking they create services
• Assuming they handle data binding

2. Which of the following is the correct syntax to create a template reference named inputBox on an <input> element?

easy

A.

B.

C.

D.

Solution

1. Step 1: Recall Angular template reference syntax

   Angular uses the hash symbol (#) to declare template references.

2. Step 2: Check each option

   Only #inputBox is valid syntax for template references on elements.

3. Final Answer:

   <input #inputBox> -> Option B

4. Quick Check:

   Use # for template references [OK]

Hint: Use # before name to create template reference [OK]

Common Mistakes:

• Using ref= instead of #
• Using * which is for structural directives
• Using $ which is invalid here

3. Given this template snippet:

<input #myInput type="text">
<button (click)="myInput.focus()">Focus</button>

What happens when the button is clicked?

medium

A. Nothing happens because focus() is not a valid method

B. An error occurs because myInput is undefined

C. The input box receives keyboard focus

D. The button text changes to 'Focus'

Solution

1. Step 1: Understand the template reference usage

   The #myInput references the input element, allowing direct access to its DOM methods.

2. Step 2: Analyze the click event

   Click calls myInput.focus(), which sets keyboard focus on the input element.

3. Final Answer:

   The input box receives keyboard focus -> Option C

4. Quick Check:

   Template ref calls focus() = input focused [OK]

Hint: Template refs access DOM methods like focus() [OK]

Common Mistakes:

• Assuming template refs are undefined in event handlers
• Thinking focus() is invalid on input elements
• Expecting button text to change

4. Consider this Angular template:

<input #userInput type="text">
<button (click)="logValue()">Log</button>

And this component code:

logValue() {
  console.log(userInput.value);
}

What is the problem here?

medium

A. The userInput template reference is not accessible in the component class

B. The logValue method is missing a parameter

C. The console.log statement is incorrect syntax

D. The button click event should be (click)="logValue(userInput)"

Solution

1. Step 1: Understand template reference scope

   Template references exist only in the template, not in the component class directly.

2. Step 2: Identify why userInput is undefined in the class

   Trying to access userInput in the class without passing it causes an error.

3. Final Answer:

   The userInput template reference is not accessible in the component class -> Option A

4. Quick Check:

   Template refs not in class scope [OK]

Hint: Template refs only exist in template, not class [OK]

Common Mistakes:

• Assuming template refs are class properties
• Forgetting to pass template ref as method argument
• Confusing template refs with ViewChild

5. You want to create a form with an input and a button that clears the input when clicked. Using a template reference #inputRef, which template code correctly implements this behavior?

hard

A.
Clear

B.
Clear

C.
Clear

D.
Clear

Solution

1. Step 1: Understand how to clear input value via template reference

   Directly setting inputRef.value = '' clears the input content.

2. Step 2: Check other options for correctness

   Options B, C, and D call undefined or non-existent methods: clear() is undefined in the component, and clear() and reset() are not methods on input elements.

3. Final Answer:

   <input #inputRef type="text"> <button (click)="inputRef.value = ''">Clear</button> -> Option A

4. Quick Check:

   Set inputRef.value to empty string to clear [OK]

Hint: Set inputRef.value = '' to clear input [OK]

Common Mistakes:

• Calling non-existent methods like clear() or reset() on input
• Trying to call component methods without passing template ref
• Confusing template ref usage with reactive forms