Laravel Get ancestors (URL)

问题

In Laravel, I have a table which contains id, parent_id, slug (Self-referring),

When I have an ID, I need to get all its ancestors in a format like this (Separated by "/").

level1/level2/level3

But in an efficient way without a package like "laravel-nestedset ".

I have implemented it like this.

public function parent()
{
    return $this->belongsTo('Collection', 'parent_id');
}

public function getParentsAttribute()
{
    $parents = collect([]);

    $parent = $this->parent;

    while(!is_null($parent)) {
        $parents->push($parent);
        $parent = $parent->parent;
    }

    return $parents;
}

Any other way to do it efficiently and separated by "/" ?

回答1:

After a little conversation in the comments I think this is a good solution:

// YourModel.php

// Add this line of you want the "parents" property to be populated all the time.
protected $appends = ['parents'];

public function getParentsAttribute()
{
    $collection = collect([]);
    $parent = $this->parent;
    while($parent) {
        $collection->push($parent);
        $parent = $parent->parent;
    }

    return $collection;
}

Then you can retrieve your parents using:

YourModel::find(123)->parents (collection instance)
YourModel::find(123)->parents->implode('yourprop', '/') (imploded to string, see https://laravel.com/docs/5.4/collections#method-implode)
YourModel::find(123)->parents->reverse()->implode('yourprop', '/') (reversed order https://laravel.com/docs/5.4/collections#method-reverse)

As noted by Nikolai Kiselev https://stackoverflow.com/a/55103589/1346367 you may also combine it with this to save a few queries:

protected $with = ['parent.parent.parent'];
// or inline:
YourModel::find(123)->with(['parent.parent.parent']);

This preloads the parent on object load. If you decide not to use this, the parent is (lazy) loaded as soon as you call $yourModel->parent.

回答2:

If you know how many levels maximum could be nested you can use Eager Loading. Let's say if maximum depth is 3 levels you can do:

$model->with('parent.parent.parent');

You can also use recursion instead of loop.

public function getParentsAttribute()
{
    if (!$this->parent) {
        return collect([]);
    }

    return collect($this->parent->parents)->push($this->parent);
}

In case you want to add the first one object too (self) the full call will be:

$model->parents->push($model)->reverse->implode('attr_name', '/');

Which you can also wrap into attribute

public function getPathAttribute() {
    return $model->parents->push($model)->reverse->implode('attr_name', '/');
}

And call like $model->path;

来源：https://stackoverflow.com/questions/55103315/laravel-get-ancestors-url

标签

php

laravel

laravel-5

eloquent