[5.4] Add the lazy method to replace the closure use in model factories

[sileence]

Following: #18499

I added the lazy method to delay the creation of models in the database in a more eloquent way:

$factory->define(App\Post::class, function (Faker\Generator $faker) {
    return [
        'user_id' => function() {
            return factory(App\User::class)->create();
        }
   ];
});

$factory->define(App\Post::class, function (Faker\Generator $faker) {
    return [
        'user_id' => factory(App\User::class)->lazy()
   ];
});

What do you think?

[taylorotwell]

Should I have to call ->create() after ->lazy()... would it be preferable to just say:

'user_id' => factory(App\User::class)->lazy(array $attributes),

[sileence]

@taylorotwell done! I thought about it after I submitted the PR 😅

[gocanto]

Can I know what is the beneffit of returning a clause?

[JosephSilber]

@gocanto https://twitter.com/joseph_silber/status/847120343022096385

[gocanto]

Yes @JosephSilber, I read your tweet as soon as it was posted. But, my question is related to the fact of returning a clausure. Why is there a reason for it? Pretty sure this is nor the place to ask this, but if it can be answered it would be nice.

[JosephSilber]

Are you sure you read that tweet carefully? It clearly explains how, without the closure, you can end up with extra models that you did not necessarily mean to create.