v-model with radio buttons in Vue - Step-by-Step Execution

Concept Flow - v-model with radio buttons

User clicks a radio button

↓

v-model updates bound variable

↓

Component re-renders with new value

↓

Radio buttons reflect selected state

When a user clicks a radio button, v-model updates the bound variable, triggering a re-render that updates which radio button appears selected.

Execution Sample

Vue

<template>
  <input type="radio" id="red" value="red" v-model="color" />
  <label for="red">Red</label>
  <input type="radio" id="blue" value="blue" v-model="color" />
  <label for="blue">Blue</label>
  <p>Selected color: {{ color }}</p>
</template>

<script setup>
import { ref } from 'vue'
const color = ref('red')
</script>

This Vue component uses v-model to bind a variable 'color' to two radio buttons, showing the selected color below.

Execution Table

Step	User Action	v-model Variable 'color'	Component Rendered Output	Radio Button Selected
1	Page loads	'red' (initial)	Selected color: red	Red radio button checked
2	User clicks 'Blue' radio button	'blue'	Selected color: blue	Blue radio button checked
3	User clicks 'Red' radio button	'red'	Selected color: red	Red radio button checked
4	User clicks 'Blue' radio button again	'blue'	Selected color: blue	Blue radio button checked
5	No further clicks	'blue'	Selected color: blue	Blue radio button checked

💡 No more user actions; variable 'color' remains 'blue' and UI reflects this.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
color	'red'	'blue'	'red'	'blue'	'blue'

Key Moments - 3 Insights

Why does clicking a radio button update the 'color' variable?

Because v-model binds the radio buttons to 'color', so when a radio button is clicked, v-model automatically sets 'color' to that button's value, as shown in execution_table steps 2 and 3.

Why does the UI text update when 'color' changes?

Vue re-renders the component when 'color' changes, updating the displayed text to match the new value, visible in the 'Component Rendered Output' column of the execution_table.

Can only one radio button be selected at a time?

Yes, radio buttons with the same v-model variable act as a group, so only one can be selected, as seen in the 'Radio Button Selected' column where only one button is checked per step.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'color' after step 3?

A 'red'

B 'blue'

C 'green'

D 'yellow'

💡 Hint

Check the 'v-model Variable 'color'' column at step 3 in the execution_table.

At which step does the 'Blue' radio button become selected?

A Step 1

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Radio Button Selected' column in the execution_table.

If the initial value of 'color' was 'blue' instead of 'red', what would be true at step 1?

A Red radio button checked

B Blue radio button checked

C No radio button checked

D Both radio buttons checked

💡 Hint

Refer to the variable_tracker and execution_table start values for 'color'.

Concept Snapshot

v-model with radio buttons binds a variable to multiple radio inputs.
When a radio button is clicked, v-model updates the variable to that button's value.
Only one radio button in the group can be selected at a time.
The UI updates reactively to show the selected value.
Use the same v-model on all radios in the group.
Labels improve accessibility and usability.

Full Transcript

This visual execution shows how Vue's v-model works with radio buttons. Initially, the variable 'color' is set to 'red', so the red radio button is selected and the text shows 'Selected color: red'. When the user clicks the blue radio button, v-model updates 'color' to 'blue', triggering a re-render that updates the displayed text and selects the blue radio button. Clicking back to red changes 'color' again, updating the UI accordingly. Only one radio button can be selected at a time because they share the same v-model variable. This example demonstrates the reactive binding and UI synchronization that v-model provides for radio button groups.

Practice

1. What does v-model do when used with radio buttons in Vue?

easy

A. It binds the selected radio button's value to a single data property.

B. It creates multiple independent data properties for each radio button.

C. It disables all radio buttons except the first one.

D. It automatically submits the form when a radio button is clicked.

Solution

1. Step 1: Understand v-model binding

   The v-model directive in Vue binds form inputs to a data property, syncing the input's value with the data.

2. Step 2: Apply to radio buttons

   For radio buttons, v-model binds the selected button's value to a single data property, so only one value is stored.

3. Final Answer:

   It binds the selected radio button's value to a single data property. -> Option A

4. Quick Check:

   v-model syncs selected radio value = C [OK]

Hint: v-model links one data value to all radios in a group [OK]

Common Mistakes:

• Thinking each radio has its own data property
• Assuming v-model disables radios
• Believing v-model auto-submits forms

2. Which of the following is the correct syntax to bind a radio button group with v-model to a data property named choice?

easy

A. <input type='radio' :model='choice' value='A'>

B. <input type='radio' v-bind='choice' value='A'>

C. <input type='radio' v-model='value' value='choice'>

D. <input type='radio' v-model='choice' value='A'>

Solution

1. Step 1: Identify correct directive usage

   The correct directive to bind input value to data is v-model, not v-bind or :model.

2. Step 2: Check attribute values

   The value attribute sets the radio's value, and v-model='choice' binds the selected value to the choice data property.

3. Final Answer:

   <input type='radio' v-model='choice' value='A'> -> Option D

4. Quick Check:

   Use v-model='choice' with value='A' = A [OK]

Hint: Use v-model='dataProp' and value='option' for radios [OK]

Common Mistakes:

• Using v-bind instead of v-model
• Swapping value and v-model attributes
• Using incorrect directive like :model

3. Given this Vue template snippet:

<template>
  <input type='radio' id='red' v-model='color' value='red'>
  <label for='red'>Red</label>
  <input type='radio' id='blue' v-model='color' value='blue'>
  <label for='blue'>Blue</label>
  <p>Selected color: {{ color }}</p>
</template>

If the user clicks the radio button labeled "Blue", what will be displayed inside the paragraph?

medium

A. Selected color: undefined

B. Selected color: red

C. Selected color: blue

D. Selected color: true

Solution

1. Step 1: Understand v-model behavior on radio buttons

   When a radio button is selected, its value is assigned to the bound data property, here color.

2. Step 2: Apply user action

   User clicks the radio with value='blue', so color becomes 'blue'. The paragraph shows this value.

3. Final Answer:

   Selected color: blue -> Option C

4. Quick Check:

   Click blue radio sets color = 'blue' [OK]

Hint: Selected radio's value updates bound data shown in template [OK]

Common Mistakes:

• Assuming initial value stays after click
• Confusing value attribute with label text
• Expecting boolean true instead of string value

4. Consider this Vue code snippet:

<input type='radio' v-model='selection' value='A'>
<input type='radio' v-model='selection' value='B'>
<input type='radio' v-model='selection' value='C'>

Why might none of the radio buttons appear selected even after clicking them?

medium

A. Radio buttons require a name attribute to work with v-model.

B. The data property selection is not initialized in the Vue component.

C. The v-model directive is misspelled.

D. The value attributes are missing from the radio buttons.

Solution

1. Step 1: Check data initialization

   Vue's v-model binds to a data property. If selection is undefined initially, no radio is selected by default.

2. Step 2: Understand radio selection behavior

   Clicking a radio sets selection to that value, but if the component does not react or update, it may be due to missing reactive data or errors elsewhere.

3. Final Answer:

   The data property selection is not initialized in the Vue component. -> Option B

4. Quick Check:

   Uninitialized data property causes no selection [OK]

Hint: Always initialize data properties used with v-model [OK]

Common Mistakes:

• Thinking name attribute is required for v-model radios
• Ignoring data property initialization
• Assuming misspelled v-model without checking

5. You want to create a group of radio buttons bound to selectedFruit with options 'Apple', 'Banana', and 'Cherry'. You also want the label text to be clickable for accessibility. Which of the following Vue template snippets correctly implements this?

hard

A. <div>
<label>
<input type='radio' v-model='selectedFruit' value='Apple'> Apple
</label>
<label>
<input type='radio' v-model='selectedFruit' value='Banana'> Banana
</label>
<label>
<input type='radio' v-model='selectedFruit' value='Cherry'> Cherry
</label>
</div>

B. <div>
<input type='radio' v-model='selectedFruit' value='Apple'>
<label>Apple</label>
<input type='radio' v-model='selectedFruit' value='Banana'>
<label>Banana</label>
<input type='radio' v-model='selectedFruit' value='Cherry'>
<label>Cherry</label>
</div>

C. <div>
<input type='radio' v-model='selectedFruit' value='Apple'> Apple
<input type='radio' v-model='selectedFruit' value='Banana'> Banana
<input type='radio' v-model='selectedFruit' value='Cherry'> Cherry
</div>

D. <div>
<input type='radio' id='apple' v-model='selectedFruit' value='Apple'> Apple
<input type='radio' id='banana' v-model='selectedFruit' value='Banana'> Banana
<input type='radio' id='cherry' v-model='selectedFruit' value='Cherry'> Cherry
</div>

Solution

1. Step 1: Understand label accessibility

   Wrapping the input inside a label makes the label text clickable and improves accessibility without needing for and id.

2. Step 2: Check the options

   <div>
     <label>
       <input type='radio' v-model='selectedFruit' value='Apple'> Apple
     </label>
     <label>
       <input type='radio' v-model='selectedFruit' value='Banana'> Banana
     </label>
     <label>
       <input type='radio' v-model='selectedFruit' value='Cherry'> Cherry
     </label>
   </div>

   wraps each radio input inside a label with the text, which is the recommended accessible pattern.

3. Final Answer:

   The snippet wrapping inputs inside <label> tags for clickable labels. -> Option A

4. Quick Check:

   Wrap input in label for clickable text = B [OK]

Hint: Wrap input inside label for easy clickable text [OK]

Common Mistakes:

• Using labels without for/id pairs
• Not wrapping input in label causing unclickable text
• Forgetting to bind v-model on each radio