Welcome to the Vue3 composable API journey! Today we are going to introduce a mysterious function: the forwardRef() function. This function is like an invisible magic wand that allows our components to become magical under certain circumstances.
First, let us understand the basic concept of forwardRef() function. In Vue, we usually use the ref() function to reference elements in a component or the component itself. However, sometimes we need to use our own references in the component, then we can use the forwardRef() function.
So, under what circumstances do you need to use forwardRef()? Imagine you are building a shopping cart component that has an area for displaying the total price. You want to abstract this area into a separate component that can be reused elsewhere. Here's the problem: this component needs to reference itself internally in order to update the total price. At this time, you need to use the forwardRef() function.
Let's look at a simple example of how to use forwardRef(). Let's say we have a component called MyComponent that needs to reference itself to update the total price:
<template>
<div>
<h2>My Component</h2>
<p>Total: {
{ total }}</p>
<button @click="increment">Increment</button>
</div>
</template>
<script>
import {
ref, forwardRef } from 'vue';
export default forwardRef(function MyComponent(props) {
const count = ref(0);
const total = ref(0);
const increment = () => {
count.value++;
total.value += 10;
};
return {
count,
total,
increment,
};
});
</script>
In this example, we use the forwardRef() function to reference the component itself. This way, we can use the ref() function inside the component to create responsive data and update the total price when needed.
Of course, the usage scenario of the forwardRef() function is not limited to this situation. It can also help us solve difficult problems in other situations, such as referencing properties of parent components in nested components.
I hope this example will give you a better understanding of the usage of the forwardRef() function. Remember, Vue3’s combined API is like a treasure. As long as we dig carefully, we can discover countless mysterious treasures!
Next, let's take a look at how to implement a complex form validation logic in Vue3. Suppose we have a registration form with multiple form fields, we need to validate each field and display an error message when appropriate.
Using the forwardRef() function, we can easily implement this functionality. First, we can create a parent component named Form and use the forwardRef() function to reference ourselves there. We can then define a method called validate() in this component to validate the form fields and display error messages.
Here is sample code to implement this functionality:
<template>
<form @submit.prevent="submit">
<div>
<label>Username:</label>
<input v-model="username" @input="validate('username')">
<span v-if="errors.username">{
{ errors.username }}</span>
</div>
<div>
<label>Password:</label>
<input v-model="password" @input="validate('password')">
<span v-if="errors.password">{
{ errors.password }}</span>
</div>
<button type="submit">Submit</button>
</form>
</template>
<script>
import {
ref, forwardRef } from 'vue';
export default forwardRef(function Form(props) {
const [username, setUsername] = ref('');
const [password, setPassword] = ref('');
const [errors, setErrors] = ref({
});
const validate = (field) => {
if (!field) {
return;
}
const value = ref(field).value;
if (value === '') {
setErrors((prev) => ({
...prev, [field]: 'Required' }));
} else if (field === 'username' && value.length < 5) {
setErrors((prev) => ({
...prev, [field]: 'Username must be at least 5 characters long' }));
} else if (field === 'password' && value.length < 8) {
setErrors((prev) => ({
...prev, [field]: 'Password must be at least 8 characters long' }));
} else {
setErrors((prev) => ({
...prev, [field]: '' }));
}
};
const submit = () => {
validate();
console.log({
username, password });
};
return {
username,
password,
errors,
validate,
submit,
};
});
</script>
In this example, we use the forwardRef() function to reference the Form component itself. Then, we defined a method called validate() in the Form component to validate the form fields and display error messages. By using the ref() function to create reactive data, we can easily update form field values and error messages.
When the user enters data, we call the validate() method to validate the field and display an error message. If the field validation passes, we use the setErrors() method to update the error message object so that it becomes an empty string. If field validation fails, we update the error message object through the setErrors() method and set its corresponding field to the corresponding error message.
I hope this example can give you a better understanding of the use of forwardRef() function in Vue3. Remember, the forwardRef() function is a very useful tool that can help us solve many complex problems and make our components more flexible, maintainable and reusable.