How to set default value in Laravel

Laravel is a PHP web application development framework that is widely popular among developers. It is known for its simplicity, elegance and excellent functionality, while also being flexible, scalable and efficient. The Laravel framework provides various developer tools and features, one of which is setting default values. Next we will focus on how to set default values ​​in the Laravel framework.

Setting Default Values ​​in Laravel

The Laravel framework provides many ways to set default values, depending on where you need to set default values. In the following sections, we'll detail how to set default values.

1. Set default values ​​in the configuration file

Laravel provides various configuration files in the config folder, such as app.php and database.php. These files typically store application-related constants and parameters. You can easily access these parameters in your application using the config function. In order to set the default value, you can define the corresponding key and value in the corresponding configuration file, as in the following example:

'welcome_message' => 'Welcome to my Laravel application!'

In this example, the key is 'welcome_message' and the value is 'Welcome to my Laravel application!'. The default value of this key is the string "Welcome to my Laravel application!"

You can use the config function to obtain this default value, and use the default value as a rollback option when accessing the welcome_message configuration value. Here is a code example to get this default value:

$message = config('app.welcome_message', 'Default welcome message');

In this example, we use the config function to get the value of the 'welcome_message' key. If the value is found, it is assigned to the $message variable. If the value is not found, the "Default welcome message" string will be used as the rollback option.

2. Set default values ​​in the model

In the Laravel framework, the model is the core of accessing the database. Models typically correspond to tables in a relational database, and they provide methods for reading, writing, and updating data in the tables. If you need to set default values ​​in the model, you can use the boot method provided by the Eloquent model. The following is an example of implementing this method:

class User extends Model 
{
    protected $fillable = [
        'name', 'email', 'password', 'phone',
    ];

    protected static function boot()
    {
        parent::boot();

        static::creating(function ($user) {
            $user->phone = $user->phone ?? '1234567890';
        });
    }
}

The boot method of this User model will be called when a new instance is created. In this example, we check the $phone property and set it to the string '1234567890' using the null coalescing operator. Every time a new User model is created, the default value of the 'phone' attribute will be '1234567890'.

3. Set default values ​​in requests

When processing HTTP requests, you may need to define default values ​​to handle parameters transmitted from the request. The Laravel framework provides multiple methods to obtain HTTP request parameters, including values ​​or corresponding returned messages.

Here, we use the Illuminate\Http\Request instance to get the HTTP request parameters. If the parameter is not found, the default value will be used, here is the example:

public function update(Request $request, $id)
{
    $name = $request->input('name', 'Lucy');
        ...
}

In this example, when the client sends the 'name' parameter to this method through the HTTP request, we use the $input method Retrieve the 'name' parameter from the $request instance. If there is no parameter named 'name', we use the 'Lucky' string as the default value.

4. Set default values ​​in the form

Finally, you may need to set default values ​​in the form to display on the HTML form component. To set default values, you can use HTML form helpers without having to hardcode HTML form elements.

{!! Form::text('name', $user->name ?? 'Lucky') !!}

In this example, we use the form helper provided by Laravel to create HTML input elements. In the parameters, we specified the name of the text box as 'name' and set 'user->name' as the default value. If 'user->name' does not exist, the 'Lucy' string is used as the default value.

Summary

In the Laravel framework, setting default values ​​is a common task. Whether in a configuration file, in a model, in a request, or in a form, the Laravel framework provides various methods to set default values ​​easily. By using the built-in functions and features of the Laravel framework, you can improve the readability, maintainability, and scalability of your application.

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