A chain of responsibility pattern practice.

README.md

用 chain of responsibility 模式實作卡路里計算公式

不過卡路里計算公式只使用了「性別」和「活動量等級」二個條件，應該不需要特地使用 design pattern 才是

實務上不需要弄得這麼複雜，當作練習就好

參考

• https://slides.com/jaceju/design-patterns-by-examples
• https://webdevetc.com/blog/the-chain-of-responsibility-programming-design-pattern-explained-using-php

AbstractCalculator.php

<?php

use App\Models\Member;

abstract class AbstractCalculator
{
    /** @var self */
    private $next = null;

    /**
     * @param  self $next
     * @return void
     */
    public function setNext(CaloriesCalculator $next)
    {
        $this->next = $next;
    }

    /**
     * @param  \App\Models\Member $member
     * @return void|\App\Models\Member
     */
    public function next(Member $member)
    {
        if ($this->next instanceof CaloriesCalculator) {
            return $this->next->calculate($member);
        }

        return $member;
    }

    /**
     * @param  \App\Models\Member $member
     * @return void
     */
    abstract public function calculate(Member $member);
}

ActivityCalculator.php

<?php

use App\Models\Member;

class ActivityCalculator extends CaloriesCalculator
{
    public function calculate(Member $member)
    {
        $ratio = 1;

        if ($member->activity === 1) {  // 低活動量
            $ratio = 1.2;
        } elseif ($member->activity === 2) {  // 中活動量
            $ratio = 1.375;
        } elseif ($member->activity === 3) {  // 高活動量
            $ratio = 1.55;
        } else {
            return $this->next($member);
        }

        $member->suggest_kcal *= $ratio;

        return $this->next($member);
    }
}

AgeCalculator.php

<?php

use App\Models\Member;
use Illuminate\Support\Carbon;

class AgeCalculator extends CaloriesCalculator
{
    public function calculate(Member $member)
    {
        $ratio = 1;

        if ($member->isMale()) {
            $ratio = 6.8;
        } elseif ($member->isFemale()) {
            $ratio = 4.7;
        } else {
            return $this->next($member);
        }

        $age = Carbon::parse($member->birthday)->age;

        $member->suggest_kcal -= ($ratio * $age);

        return $this->next($member);
    }
}

BmrCalculator.php

<?php

use App\Models\Member;

class BmrCalculator extends CaloriesCalculator
{
    public function calculate(Member $member)
    {
        if ($member->isMale()) {
            $member->suggest_kcal += 66;
        } elseif ($member->isFemale()) {
            $member->suggest_kcal += 665;
        } else {
            return $this->next($member);
        }

        return $this->next($member);
    }
}

example.php

<?php

$step1 = new HeightCalculator();
$step2 = new WeightCalculator();
$step3 = new AgeCalculator();
$step4 = new BmrCalculator();
$step5 = new ActivityCalculator();

// 基礎代謝率 Basal metabolic rate
$step1->setNext($step2);
$step2->setNext($step3);
$step3->setNext($step4);
$memberWithBmr = $step1->calculate($member);

// 每日建議攝取熱量 Recommended daily calories
$step4->setNext($step5);
$memberWithRdc = $step4->calculate($memberWithBmr);

HeightCalculator.php

<?php

use App\Models\Member;

class HeightCalculator extends AbstractCalculator
{
    public function calculate(Member $member)
    {
        $ratio = 1;

        if ($member->isMale()) {
            $ratio = 13.7;
        } elseif ($member->isFemale()) {
            $ratio = 9.6;
        } else {
            return $this->next($member);
        }

        $member->suggest_kcal += ($ratio * $member->height);

        return $this->next($member);
    }
}

Member.php

<?php

use Illuminate\Database\Eloquent\Model;

class Member extends Model
{
    public function isMale()
    {
        // ...
    }

    public function isFemale()
    {
        // ...
    }
}

WeightCalculator.php

<?php

use App\Models\Member;

class WeightCalculator extends AbstractCalculator
{
    public function calculate(Member $member)
    {
        $ratio = 1;

        if ($member->isMale()) {
            $ratio = 5;
        } elseif ($member->isFemale()) {
            $ratio = 1.8;
        } else {
            return $this->next($member);
        }

        $member->suggest_kcal += ($ratio * $member->weight);

        return $this->next($member);
    }
}