87 lines
2.8 KiB
Markdown
87 lines
2.8 KiB
Markdown
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# FieldNotify
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- **功能描述：** 在打开MVVM插件后，使得该属性变成支持FieldNotify的属性。
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- **元数据类型：** bool
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- **引擎模块：** MVVM, UHT
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- **限制类型：** ViewModel里的属性
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- **常用程度：** ★★★★
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在打开MVVM插件后，使得该属性变成支持FieldNotify的属性。
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## 测试代码：
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```cpp
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UCLASS(BlueprintType)
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class INSIDER_API UMyViewModel :public UMVVMViewModelBase
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{
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GENERATED_BODY()
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protected:
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UPROPERTY(BlueprintReadWrite, FieldNotify, Getter, Setter, BlueprintSetter = SetHP)
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float HP = 1.f;
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UPROPERTY(BlueprintReadWrite, FieldNotify, Getter, Setter, BlueprintSetter = SetMaxHP)
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float MaxHP = 100.f;
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public:
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float GetHP()const { return HP; }
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UFUNCTION(BlueprintSetter)
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void SetHP(float val)
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{
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if (UE_MVVM_SET_PROPERTY_VALUE(HP, val))
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{
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UE_MVVM_BROADCAST_FIELD_VALUE_CHANGED(GetHPPercent);
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}
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}
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float GetMaxHP()const { return MaxHP; }
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UFUNCTION(BlueprintSetter)
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void SetMaxHP(float val)
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{
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if (UE_MVVM_SET_PROPERTY_VALUE(MaxHP, val))
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{
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UE_MVVM_BROADCAST_FIELD_VALUE_CHANGED(GetHPPercent);
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}
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}
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//You need to manually notify that GetHealthPercent changed when CurrentHealth or MaxHealth changed.
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UFUNCTION(BlueprintPure, FieldNotify)
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float GetHPPercent() const
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{
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return (MaxHP != 0.f) ? HP / MaxHP : 0.f;
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}
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};
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```
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## 测试效果：
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效果一方面是UHT生成的.generated.h里和.gen.cpp里的代码，具体的宏作用就不展开了，大家可查看其他更细致的MVVM相关文章。这里只要知道UHT会为标了FieldNotify的属性定义FFieldId以及FFieldNotificationClassDescriptor来标识一个接受可通知的属性。
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```cpp
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//MyViewModel.generated.h
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#define FID_GitWorkspace_Hello_Source_Insider_Property_MVVM_MyViewModel_h_12_FIELDNOTIFY \
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UE_FIELD_NOTIFICATION_DECLARE_CLASS_DESCRIPTOR_BEGIN(INSIDER_API ) \
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UE_FIELD_NOTIFICATION_DECLARE_FIELD(HP) \
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UE_FIELD_NOTIFICATION_DECLARE_FIELD(MaxHP) \
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UE_FIELD_NOTIFICATION_DECLARE_FIELD(GetHPPercent) \
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UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD_BEGIN(HP) \
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UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD(MaxHP) \
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UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD(GetHPPercent) \
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UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD_END() \
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UE_FIELD_NOTIFICATION_DECLARE_CLASS_DESCRIPTOR_END();
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//MyViewModel.gen.cpp
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UE_FIELD_NOTIFICATION_IMPLEMENT_FIELD(UMyViewModel, HP)
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UE_FIELD_NOTIFICATION_IMPLEMENT_FIELD(UMyViewModel, MaxHP)
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UE_FIELD_NOTIFICATION_IMPLEMENT_FIELD(UMyViewModel, GetHPPercent)
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UE_FIELD_NOTIFICATION_IMPLEMENTATION_BEGIN(UMyViewModel)
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UE_FIELD_NOTIFICATION_IMPLEMENT_ENUM_FIELD(UMyViewModel, HP)
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UE_FIELD_NOTIFICATION_IMPLEMENT_ENUM_FIELD(UMyViewModel, MaxHP)
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UE_FIELD_NOTIFICATION_IMPLEMENT_ENUM_FIELD(UMyViewModel, GetHPPercent)
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UE_FIELD_NOTIFICATION_IMPLEMENTATION_END(UMyViewModel);
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```
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蓝图效果：
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这些控件的属性就可以和ViewModel里的属性绑定起来。
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