Use forwardRef function in Vue3 combination API

Welcome to Vue3's combined API journey! Today we are going to introduce a mysterious function: the forwardRef() function. This function is like an invisible magic wand that makes our components powerful in some cases.

First, let's understand the basic concept of forwardRef() function. In Vue, we usually use the ref() function to refer to an element in a component or the component itself. However, sometimes we need to use our own references in the component, and 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 with an area for displaying the total price. You want to abstract this area into a separate component for reuse elsewhere. The problem is: 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(). Suppose we have a component called MyComponent which 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 = () => {  
    ++;  
     += 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 if needed.

Of course, the use scenarios of forwardRef() function are not limited to this situation. It can also help us solve problems in other situations, such as referencing the properties of the parent component in a nested component, etc.

Hopefully this example will help you better understand the usage of forwardRef() function. Remember, Vue3's combination 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 verification logic in Vue3. Suppose we have a registration form with multiple form fields, we need to verify each field and display an error message when appropriate.

Using the forwardRef() function, we can easily implement this function. First, we can create a parent component called Form and use the forwardRef() function to reference ourselves. We can then define a method called validate() in this component to validate the form field and display an error message.

Here is the example code to implement this function:

<template>  
  <form @="submit">  
    <div>  
      <label>Username:</label>  
      <input v-model="username" @input="validate('username')">  
      <span v-if="">{{  }}</span>  
    </div>  
    <div>  
      <label>Password:</label>  
      <input v-model="password" @input="validate('password')">  
      <span v-if="">{{  }}</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' &&  < 5) {  
      setErrors((prev) => ({ ...prev, [field]: 'Username must be at least 5 characters long' }));  
    } else if (field === 'password' &&  < 8) {  
      setErrors((prev) => ({ ...prev, [field]: 'Password must be at least 8 characters long' }));  
    } else {  
      setErrors((prev) => ({ ...prev, [field]: '' }));  
    }  
  };  
  const submit = () => {  
    validate();  
    ({ username, password });  
  };  
  return {  
    username,  
    password,  
    errors,  
    validate,  
    submit,  
  };  
});  
</script>

In this example, we use the forwardRef() function to reference the Form component itself. We then define a method called validate() in the Form component to validate the form field and display an error message. By using the ref() function to create responsive data, we can easily update the value and error messages of form fields.

When the user enters data, we call the validate() method to verify the field and display an error message. If the field verification passes, we update the error message object through the setErrors() method to make it an empty string. If field verification fails, we update the error message object through the setErrors() method and set its corresponding field to the corresponding error message.

Hopefully this example will help you better understand the use of forwardRef() function in Vue3. Remember, the forwardRef() function is a very useful tool that can help us solve many complex problems, making our components more flexible, maintainable and reusable.

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