54 lines
1.9 KiB
Markdown
54 lines
1.9 KiB
Markdown
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# FieldNotifyInterfaceParam
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- **功能描述：** 指定函数的某个参数提供FieldNotify的ViewModel信息。
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- **使用位置：** UFUNCTION
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- **引擎模块：** FieldNotify
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- **元数据类型：** string="abc"
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- **限制类型：** 函数里有其他FFieldNotificationId 参数
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- **常用程度：** ★★★
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指定函数的某个参数提供FieldNotify的ViewModel信息。
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该参数为之后的FFieldNotificationId参数的提供上下文信息，这样FieldId的选项框才知道有哪些可选值。
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## 源码例子：
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```cpp
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/** Broadcast that the Field value changed. */
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UFUNCTION(BlueprintCallable, Category = "FieldNotification", meta = (FieldNotifyInterfaceParam="Object", DisplayName = "Broadcast Field Value Changed"))
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static void BroadcastFieldValueChanged(UObject* Object, FFieldNotificationId FieldId);
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```
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## 蓝图效果：
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在UserWidget里测试，可见没有连接到参数的Target默认为当前的UserWidget，则FieldId是3个值。而连接到我们自定义的ViewModel后，则改变为我们下面定义的值。
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## 原理：
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```cpp
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TSharedRef<SWidget> SFieldNotificationGraphPin::GetDefaultValueWidget()
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{
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UEdGraphPin* SelfPin = GraphPinObj->GetOwningNode()->FindPin(UEdGraphSchema_K2::PSC_Self);
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if (UK2Node_CallFunction* CallFunction = Cast<UK2Node_CallFunction>(GraphPinObj->GetOwningNode()))
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{
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if (UFunction* Function = CallFunction->GetTargetFunction())
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{
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const FString& PinName = Function->GetMetaData("FieldNotifyInterfaceParam");
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if (PinName.Len() != 0)
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{
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SelfPin = GraphPinObj->GetOwningNode()->FindPin(*PinName);
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}
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}
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}
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return SNew(SFieldNotificationPicker)
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.Value(this, &SFieldNotificationGraphPin::GetValue)
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.OnValueChanged(this, &SFieldNotificationGraphPin::SetValue)
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.FromClass_Static(Private::GetPinClass, SelfPin)
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.Visibility(this, &SGraphPin::GetDefaultValueVisibility);
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}
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```
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