Laravel 5 - 雄辩模型 - 3个系列表

Question

Scenario - I have 3 tables > Country, State, City. City have stateid column, State have countryid column, country have no reference.

City Model methods

public function state(){ 
    return $this->belongsTo('App\State', 'stateid');
}

State Model methods

public function country(){
    return $this->belongsTo('App\Country', 'countryid');
}
public function cities(){
    return $this->hasMany('App\City', 'stateid');
}

Country Model methods

public function states()
{
    return $this->hasMany('App\State', 'countryid');
}

Problem - I want to get the list of cities in a country. How can I create a method in Country Model like this? -

public function cities(){
    return $this->states()->cities(); //Calling hasMany on builder is not possible.
}

Similarly, a method to country name from city model.

Answer 1

To retrieve a Collection with all cities in a Country, use the hasManyThrough method:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Country extends Model
{
    public $timestamps = false;

    public function states()
    {
        return $this->hasMany(State::class);
    }

    public function cities()
    {
        return $this->hasManyThrough(City::class, State::class);
    }
}