歐文的BLOG

建造者模式(Builder Pattern)

不同於工場模式，給一些生成要求而產生目標物件

（ex: 以遊戲舉例，跟兵工廠說, 我要弓箭手, 工廠就把弓箭手給你）

若有太多客制項目，工廠要為了這些該怎麼辦

如：我要一個有紅色弓箭的弓箭手，且要女的，身材很好，年歲.... 一大堆條件．

對於工廠來說他只要產生弓箭手！ 其餘的他不管...

上面只個例子，主要強調針對太多客制項目的時候，該怎麼處裡呢？

Builder Pattern 就是一個可參考的設計模型

以下我以包子舉例好了

有個包子工廠專門生產包子

如肉包, 菜包, 素包等常見的肉包

但我這個客人很奇怪，嘴很挑，想吃點山珍海味的包子（魚翅包子啊, 開口笑包子之類的）

對包子工廠來說，就需要一直開很多建構式或者type來處理．

若我想要一個魚翅包子，那不就要新增或修改工廠裡面的項目嘛？

對使用者來說，我只要個特別餡料的包子而已，還要研究整個包子工廠運作，會不會太麻煩！！！

這時候就可以使用builder pattern了

讓使用者自行客制所需要的內容

工廠根據內容再產生需求的包子，讓使用者簡單操作

以下是個簡單的範例

我用手機來舉例, 或許大家比較有感

有個手機工廠 可以產生很多種類的手機

有ios, android, windows phone 三種系統

也可以根據需求來客制裝置

程式碼如下：

package com.owen.blogapp;

import java.lang.ref.WeakReference;
import java.util.Locale;

/**
 * Created by owen on 2017/11/19.
 */

public class Phone {

    private enum TYPE {IOS, ANDROID, WINDOW_PHONE, OTHER}

    private TYPE mType;
    private boolean mWifi;
    private boolean mBluetooth;
    private int mMemorySize;
    private int mDiskSize;
    private int mPowerSize;
    private Locale mLocale;
    private String mDefaultInput;
    private String[] mOther;

    public Phone(){}

    public Phone(TYPE mType, boolean mWifi, boolean mBluetooth,
                 int mMemorySize, int mDiskSize, int mPowerSize,
                 Locale mLocale, String mDefaultInput, String[] mOther, String... other) {
        this.mType = mType;
        this.mWifi = mWifi;
        this.mBluetooth = mBluetooth;
        this.mMemorySize = mMemorySize;
        this.mDiskSize = mDiskSize;
        this.mPowerSize = mPowerSize;
        this.mLocale = mLocale;
        this.mDefaultInput = mDefaultInput;
        this.mOther = mOther;
    }

    public TYPE getType() {
        return mType;
    }

    public void setType(TYPE mType) {
        this.mType = mType;
    }

    public boolean ismWifi() {
        return mWifi;
    }

    public void setWifi(boolean mWifi) {
        this.mWifi = mWifi;
    }

    public boolean ismBluetooth() {
        return mBluetooth;
    }

    public void setBluetooth(boolean mBluetooth) {
        this.mBluetooth = mBluetooth;
    }

    public int getMemorySize() {
        return mMemorySize;
    }

    public void setMemorySize(int mMemorySize) {
        this.mMemorySize = mMemorySize;
    }

    public int getDiskSize() {
        return mDiskSize;
    }

    public void setDiskSize(int mDiskSize) {
        this.mDiskSize = mDiskSize;
    }

    public int getPowerSize() {
        return mPowerSize;
    }

    public void setPowerSize(int mPowerSize) {
        this.mPowerSize = mPowerSize;
    }

    public Locale getLocale() {
        return mLocale;
    }

    public void setLocale(Locale mLocale) {
        this.mLocale = mLocale;
    }

    public String getDefaultInput() {
        return mDefaultInput;
    }

    public void setDefaultInput(String mDefaultInput) {
        this.mDefaultInput = mDefaultInput;
    }

    public String[] getOther() {
        return mOther;
    }

    public void setOther(String[] mOther) {
        this.mOther = mOther;
    }

    public static class Builder {

        private WeakReference mWType;
        private WeakReference mWWifi;
        private WeakReference mWBluetooth;
        private WeakReference mWMemorySize;
        private WeakReference mWDiskSize;
        private WeakReference mWPowerSize;
        private WeakReference mWLocale;
        private WeakReference mWDefaultInput;
        private WeakReference mWOther;

        public Builder setType(TYPE type) {
            mWType = new WeakReference<>(type);
            return this;
        }

        public Builder setWifiEnable(boolean wifiEnable) {
            mWWifi = new WeakReference<>(wifiEnable);
            return this;
        }

        public Builder setBTEnable(boolean setBTEnable) {
            mWBluetooth = new WeakReference<>(setBTEnable);
            return this;
        }

        public Builder setemorySize(int size) {
            mWMemorySize = new WeakReference<>(size);
            return this;
        }

        public Builder setDiskSize(int diskSize) {
            mWDiskSize = new WeakReference<>(diskSize);
            return this;
        }

        public Builder setPowerSize(int powerSize) {
            mWPowerSize = new WeakReference<>(powerSize);
            return this;
        }

        public Builder setLocale(Locale locale) {
            mWLocale = new WeakReference<>(locale);
            return this;
        }

        public Builder setDefaultInput(String defaultInput) {
            mWDefaultInput = new WeakReference<>(defaultInput);
            return this;
        }

        public Builder setOther(String... other) {
            mWOther = new WeakReference<>(other);
            return this;
        }

        public Phone build() {
            Phone phone = new Phone();
            if (mWType != null && mWType.get()!= null){
                phone.setType(mWType.get());
            }

            if (mWBluetooth != null && mWBluetooth.get()!= null){
                phone.setBluetooth(mWBluetooth.get());
            }

            if (mWMemorySize != null && mWMemorySize.get()!= null){
                phone.setMemorySize(mWMemorySize.get());
            }

            if (mWDiskSize != null && mWDiskSize.get()!= null){
                phone.setDiskSize(mWDiskSize.get());
            }

            if (mWPowerSize != null && mWPowerSize.get()!= null){
                phone.setPowerSize(mWPowerSize.get());
            }

            if (mWLocale != null && mWLocale.get()!= null){
                phone.setLocale(mWLocale.get());
            }

            if (mWDefaultInput != null && mWDefaultInput.get()!= null){
                phone.setDefaultInput(mWDefaultInput.get());
            }

            if (mWOther != null && mWOther.get()!= null){
                phone.setOther(mWOther.get());
            }

            return phone;
        }
    }
}

整個程式碼有個好處, 不用針對部分需求建立建構式...