第十一章:构型境 · 设计模式之道
"千术可构,格局需明;结构得法,道可延年。"
顾行云正式承担"魂核驱动阵"的重构之任,发现需求纷繁、参数繁多、状态变化复杂。传统术式难以胜任,他遂投身于构型殿修行,悟得三种典范设计法术。
一、建造之术 · Builder Pattern
用于灵术属性繁多、创建步骤复杂的情况
症状:构建灵器时参数众多、混乱:
rust
let blade = SoulBlade {
name: String::from("斩灵"),
element: Some(Element::Fire),
weight: None,
enchant_level: Some(3),
};
太难维护,灵力失衡......
Builder 解法:
rust
struct SoulBlade {
name: String,
element: Option<Element>,
enchant_level: Option<u32>,
}
struct SoulBladeBuilder {
blade: SoulBlade,
}
impl SoulBladeBuilder {
fn new(name: &str) -> Self {
Self { blade: SoulBlade {
name: name.to_string(),
element: None,
enchant_level: None,
}}
}
fn element(mut self, e: Element) -> Self {
self.blade.element = Some(e);
self
}
fn enchant_level(mut self, lv: u32) -> Self {
self.blade.enchant_level = Some(lv);
self
}
fn build(self) -> SoulBlade {
self.blade
}
}
使用:
rust
let blade = SoulBladeBuilder::new("焰牙")
.element(Element::Fire)
.enchant_level(2)
.build();
"构建之术,柔中带钢;既可明确流程,又不扰主结构。"
二、策略之术 · Strategy Pattern
用于行为可变、规则常换的灵法模块
顾行云设计"伤害计算系统",不同灵兽使用不同算法:
rust
trait DamageStrategy {
fn calculate(&self, base: u32) -> u32;
}
struct FireDamage;
impl DamageStrategy for FireDamage {
fn calculate(&self, base: u32) -> u32 { base + 20 }
}
struct IceDamage;
impl DamageStrategy for IceDamage {
fn calculate(&self, base: u32) -> u32 { base + 10 }
}
召唤统一接口:
rust
fn apply_damage(s: &dyn DamageStrategy, base: u32) {
println!("最终伤害:{}", s.calculate(base));
}
"策略可换,接口不改。既统则固,可换则柔。"
三、状态之术 · State Pattern
适用于灵器/咒术状态多变、切换行为不同之术
顾行云构建"法术卷轴",可处于三种状态:未解封、激活中、冷却中
设计如下:
rust
trait ScrollState {
fn use_scroll(&self) -> Box<dyn ScrollState>;
}
struct Sealed;
struct Active;
struct Cooldown;
impl ScrollState for Sealed {
fn use_scroll(&self) -> Box<dyn ScrollState> {
println!("解封卷轴!");
Box::new(Active)
}
}
impl ScrollState for Active {
fn use_scroll(&self) -> Box<dyn ScrollState> {
println!("施术完成,进入冷却。");
Box::new(Cooldown)
}
}
impl ScrollState for Cooldown {
fn use_scroll(&self) -> Box<dyn ScrollState> {
println!("卷轴冷却中,无法使用。");
Box::new(Cooldown)
}
}
struct SpellScroll {
state: Box<dyn ScrollState>,
}
impl SpellScroll {
fn new() -> Self {
Self { state: Box::new(Sealed) }
}
fn activate(&mut self) {
self.state = self.state.use_scroll();
}
}
"术随境迁,道应时通。"
构型心法
术有形者,必有格局;格局清明者,方可纳万变。