【設計模式與Android】建造者模式——建軍大業

時間 2020-01-01

原文原文鏈接

什麼是建造者模式設計模式

所謂建造者模式，就是將一個複雜對象的構建與它的表示分離，使得一樣的構建過程能夠建立不一樣的表示的設計模式。建造者模式在構建過程當中隱藏了複雜的實現細節，能夠大大下降代碼耦合度。ide

建造者模式的實現方式oop

《水滸傳》講述了的故事，梁山泊是一個不斷壯大的隊伍ui

先寫一個Troops：this

public abstract class Troops {

    protected String leader;
    protected ArrayList<String> others = new ArrayList<>();
    protected String purpose;

    //領袖
    public void setLeader(String leader) {
        this.leader = leader;
    }

    //其餘人
    public void setOthers(String... others) {
        for (String other:others){
            this.others.add(other);
        }
    }

    //宗旨
    public abstract void setPurpose();

    @Override
    public String toString() {
        return "Troops{" +
                "leader='" + leader + '\'' +
                ", others=" + others.toString() +
                ", purpose='" + purpose + '\'' +
                '}';
    }
}spa

這是梁山的Troops：設計

public class Liangshan extends Troops {

    protected Liangshan(){}

    @Override
    public void setPurpose() {
        purpose = "替天行道";
    }
}orm

再寫一個Builder：對象

public abstract class Builder {

    public abstract void buildLeader(String leader);

    public abstract void buildOthers(String... others);

    public abstract void buildPurpose();

    public abstract Troops create();

}blog

這是好漢們的Builder：

public class LiangshanBuilder extends Builder {

    private Liangshan liangshan;

    @Override
    public void buildLeader(String leader) {
        liangshan.setLeader(leader);
    }

    @Override
    public void buildOthers(String... others) {
        liangshan.setOthers(others);
    }

    @Override
    public void buildPurpose() {
        liangshan.setPurpose();
    }

    @Override
    public Troops create() {
        return liangshan;
    }
}

接下來寫一個Director：

public class Director {

    Builder mBuilder = null;

    public Director(Builder builder){
        this.mBuilder = builder;
    }

    public void construct(String leader,String... others){
        mBuilder.buildLeader(leader);
        mBuilder.buildOthers(others);
        mBuilder.buildPurpose();
    }

}

咱們只須要以下代碼即可以實現梁山好漢的大聚義：

Builder builder = new LiangshanBuilder();
Director director = new Director(builder);
director.construct("宋江","盧俊義","吳用","公孫勝");
Log.e("梁山",builder.create().toString());

在實際開發過程當中，Director層經常被省略，由一個鏈式調用的Builder來進行對象的組裝。咱們此次用梁山好漢的對立面——方臘來舉例，此次這麼改寫上文的Builder：

public class MingjiaoBuilder{
    private Mingjiao mingjiao;

    public MingjiaoBuilder(){
        mingjiao = new Mingjiao();
    }

    public MingjiaoBuilder buildLeader(String leader) {
        mingjiao.setLeader(leader);
        return this;
    }

    public MingjiaoBuilder buildOthers(String... others) {
        mingjiao.setOthers(others);
        return this;
    }

    public MingjiaoBuilder buildPurpose() {
        mingjiao.setPurpose();
        return this;
    }

    public Mingjiao create() {
        return mingjiao;
    }
}

固然，Troops是這樣繼承的：

public class Mingjiao extends Troops {
    @Override
    public void setPurpose() {
        this.purpose = "做亂犯上";
    }
}

而後方臘做亂犯上的過程是這樣的：

MingjiaoBuilder builder = new MingjiaoBuilder()
        //雖是妄稱天子位
        .buildLeader("方臘")
        //也須僞列宰臣班
        .buildOthers("石寶","鄧元覺","方傑")
        .buildPurpose();
Log.e("明教",builder.create().toString());