86 lines
2.4 KiB
Markdown
86 lines
2.4 KiB
Markdown
---
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title: UE5 MVVM 笔记
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date: 2025-08-26 10:05:44
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excerpt:
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tags:
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rating: ⭐
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---
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# 前言
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- 知乎文章
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- [UE5.6新功能MVVM使用方式（从笔记里迁移）](https://zhuanlan.zhihu.com/p/1918763422243325641)
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-
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# Example
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```c++
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UCLASS(Blueprintable)
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class UMyViewModelBase : public UMVVMViewModelBase
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{
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GENERATED_BODY()
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private:
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// FieldNotify：使得属性可以用于通知广播
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// Setter:此属性可以被设置，Setter函数的名称格式 Set[Variable Name],CurrentHealth的Setter为：SetCurrentHealth
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// Setter = [Function Name] 也可以自己指定名称，写法如前
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// Getter:此属性可以被获取，Getter函数的名称格式为 Get[Variable Name],CurrentHealth的Getter为：GetCurrentHealth
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// Getter = [Function Name] 也可以自己指定名称，写法如前
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// 此字段在ViewModel中使用Get/Set访问，在蓝图中是Public的，在蓝图中ViewBanding使用Get/Set
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UPROPERTY(BlueprintReadWrite, FieldNotify, Setter, Getter, meta=(AllowPrivateAccess))
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int32 CurrentHealth;
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UPROPERTY(BlueprintReadWrite, FieldNotify, Setter, Getter, meta=(AllowPrivateAccess))
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int32 MaxHealth;
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public:
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void SetCurrentHealth(int32 NewCurrentHealth)
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{
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if (UE_MVVM_SET_PROPERTY_VALUE(CurrentHealth, NewCurrentHealth))
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{
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UE_MVVM_BROADCAST_FIELD_VALUE_CHANGED(GetHealthPercent);
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}
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}
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void SetMaxHealth(int32 NewMaxHealth)
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{
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// 内部是一个模版函数，有特化版本，最终作用是做compare并触发Boradcast
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// 原理也一样，就是通过名字传递Property做compare，
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// 然后通过名字拿到Fiedld取Delegate进行boradcast
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// ([Variable Name][NewValue])
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if (UE_MVVM_SET_PROPERTY_VALUE(MaxHealth, NewMaxHealth))
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{
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// 如果MaxHealth改变了，HealthPercent也需要更新
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// 内部通过名称拿到一个FieldId，然后通过FieldId找到对应的Delegate进行Boradcast
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UE_MVVM_BROADCAST_FIELD_VALUE_CHANGED(GetHealthPercent);
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}
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}
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int32 GetCurrentHealth() const
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{
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return CurrentHealth;
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}
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int32 GetMaxHealth() const
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{
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return MaxHealth;
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}
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public:
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/**
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* 必须具有带 FieldNotify 和 BlueprintPure 说明符的 UFUNCTION 宏。
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* 不得带有参数。
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* 必须是 const 函数。
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* 必须仅返回单个值（没有输出参数）。
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* @return
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*/
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UFUNCTION(BlueprintPure, FieldNotify)
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float GetHealthPercent() const
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{
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if (MaxHealth != 0)
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{
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return (float) CurrentHealth / (float) MaxHealth;
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}
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else
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return 0;
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}
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};
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``` |