Now, let’s talk about communication between components. Especially in modern frameworks like Vue.js, these things can sometimes be a bit confusing, honestly. It’s like performing a magic trick where everything suddenly falls into place — capturing those moments is important. When we want to pass something from a child component to a parent component, we need to build that bridge. This is where custom events come into play, exactly what we need! 🙂
As I mentioned before, component communication can seem complicated at first. Especially when developing a REST API with C# on the backend and working with a dynamic front-end like Vue.js, maintaining synchronization is almost an art. Think of it like a puzzle; when all pieces fit perfectly, the whole becomes satisfying. In this article, I will explain how to cleanly and understandably transfer data from child to parent in Vue.js using custom events. We will also touch on how to integrate this with a C# API.
First, let’s look at how things work on the Vue.js side. Normally, to pass data from parent to child, we use props. But when it comes to sending data from child to parent, props alone are not enough. This is where custom events rescue us. By communicating through Vue’s event system, we can push the desired data from child to parent. I’ve used this method many times in my projects and it really works well.
So, how do we use these custom events? Simply put, inside the child component, we call the `$emit` function in a method. This function takes the name of the event we want to send as its first argument, and subsequent arguments are the data we wish to pass along. For example, if we want to send data upon clicking a button, we write a function tied to the click event that calls `$emit(‘sendData’, dataToSend)`. That’s all there is to it.
Let’s clarify this with an example. Suppose we have a form that creates a user profile. This form is the child component. After filling out the form, we want to send this information to the parent component to be saved, for example, in an API. Initially, we might think of something like this:
// Child Component (UserProfileForm.vue)
Such a template:
<template>
<div>
<input type=”text” v-model=”userName” placeholder=”Username” />
<input type=”email” v-model=”userEmail” placeholder=”Email” />
<button @click=”save”>Save</button>
</div>
</template>
And in the script part:
<script>
export default {
data() {
return {
userName: ”,
userEmail: ”
};
},
methods: {
save() {
const userData = { name: this.userName, email: this.userEmail };
// Here, we trigger the custom event
this.$emit(‘userSaved’, userData);
}
}
}
</script>
When the save method is clicked in this child component, an event called `userSaved` is emitted with an object containing the user’s name and email. Isn’t that nice?
Now, how do we catch this event in the parent component? The parent might look like this:
// Parent Component (App.vue)
<template>
<div>
<h1>User Registration</h1>
<UserProfileForm @userSaved=”saveUser” />
<p v-if=”savedUser”>Saved: {{ savedUser.name }} – {{ savedUser.email }}</p>
</div>
</template>
<script>
import UserProfileForm from ‘./components/UserProfileForm.vue’;
export default {
components: {
UserProfileForm
},
data() {
return {
savedUser: null
};
},
methods: {
saveUser(userData) {
console.log(‘Parent: User saved!’, userData);
this.savedUser = userData;
// Here, data can be sent to a C# API
// For example, using fetch or axios to make a POST request
// Example: this.sendToApi(userData);
}
// sendToApi(data) { … } // API call method goes here
}
}
</script>
The key point here is to add an event listener like `@userSaved=”saveUser”` when using `UserProfileForm` component. This ensures that when the child component emits the `userSaved` event, the `saveUser` method in the parent is called. And the user data from child is automatically passed as the parameter. That’s it, so simple.
This approach is really practical. Although it might seem intimidating at first, after a few trials, it becomes straightforward. It’s all about setting up an event-driven structure — when something happens, notify others and let them react accordingly.
Now, let’s consider the C# side. Suppose we are going to send the user information collected via Vue.js to an ASP.NET Core Web API, which will then save it to a database. This involves receiving the `userData` object from child, converting it into a C# DTO (Data Transfer Object), and storing it in PostgreSQL. Using Dapper ORM makes this process faster and easier.
First, define a DTO:
// DTO (KullaniciDto.cs)
public class KullaniciDto {
public string Name { get; set; }
public string Email { get; set; }
}Then, in the controller, write a POST method that accepts this DTO:
// Controller (KullaniciController.cs)
[Route("api/[controller]")] [ApiController] public class KullaniciController : ControllerBase {
private readonly string _connectionString = "Server=localhost;Database=MyDb;User Id=postgres;Password=password"; // UPDATE TO YOUR DATABASE DETAILS! [HttpPost]
public async Task PostKullanici([FromBody] KullaniciDto kullanici) {
if (kullanici == null) {
return BadRequest("Invalid user data.");
}
try {
using (var connection = new NpgsqlConnection(_connectionString)) {
connection.Open();
// Use Dapper for INSERT query
// Example:
// await connection.ExecuteAsync("INSERT INTO Users (Name, Email) VALUES (@Name, @Email)", kullanici);
// For simplicity, just log to console for now
Console.WriteLine($"User saved: {kullanici.Name}, {kullanici.Email}");
}
return Ok(new { message = "User successfully saved." });
} catch (Exception ex) {
// Proper logging should be done in real projects
return StatusCode(500, $"An error occurred: {ex.Message}");
}
} }
This controller method will automatically map the incoming JSON data to the `KullaniciDto` object. After that, you can proceed to save it into the database. While it seems a bit complex initially, the logic is simple — transferring data from one point to another.
Under the hood, the main idea is that Vue.js’s `$emit` triggers events, and on the C# side, there is an API endpoint listening via HTTP POST requests. These two technologies communicate seamlessly. Isn’t that neat?
In conclusion, custom events in Vue.js offer a great solution for transferring data from child to parent components. Using Vue’s `$emit`, you can easily handle this and forward data to your C# API backend. This allows different layers of your app to communicate smoothly. After all, the goal is to keep your application modular and maintainable, isn’t it?
If you want more details, you can check the official documentation on Vue.js custom events. For C# and Dapper usage in PostgreSQL, visit Dapper’s GitHub page. There are also many good YouTube videos on this topic, search for here.