Fortnite Verse代码初始化slider_regular报错，DefaultValue写法问题排查

我在Unreal Engine For Fortnite环境下进行Verse代码开发时遇到了编译报错。以下是我的代码：

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /UnrealEngine.com/Temporary/UI }
using { /Fortnite.com/UI }
using { /UnrealEngine.com/Temporary/SpatialMath }

CustomHP := class(creative_device):

    @editable
    Button:button_device = button_device{}

    OnBegin<override>()<suspends> : void =
        Button.InteractedWithEvent.Subscribe(HandleButtonInteraction)

    HandleButtonInteraction(Agent : agent) : void =
        if (InPlayer := player[Agent], PlayerUI := GetPlayerUI[InPlayer]):
            MyUI : slider_regular = slider_regular {DefaultValue:float := 100.0, DefaultMinValue:float := 0.0, DefaultMaxValue:float := 100.0, DefaultStepSize:float := 1.0}
            PlayerUI.AddWidget(MyUI)

编译返回的错误信息如下：

C:/Users/BraveGamerTV/Documents/Fortnite Projects/MyProject/Plugins/MyProject/Content/CustomHP.verse(17,66, 17,71) : Script error 3577: Unexpected expression
C:/Users/BraveGamerTV/Documents/Fortnite Projects/MyProject/Plugins/MyProject/Content/CustomHP.verse(17,98, 17,103) : Script error 3577: Unexpected expression
C:/Users/BraveGamerTV/Documents/Fortnite Projects/MyProject/Plugins/MyProject/Content/CustomHP.verse(17,128, 17,133) : Script error 3577: Unexpected expression
C:/Users/BraveGamerTV/Documents/Fortnite Projects/MyProject/Plugins/MyProject/Content/CustomHP.verse(17,160, 17,165) : Script error 3577: Unexpected expression

问题原因与解决方案 #

报错是因为初始化slider_regular时，错误地给属性添加了:float这类类型注解。Verse的对象初始化语法不支持这种写法——slider_regular类的属性类型已经在类定义中确定，编译器会自动推导值的类型，无需手动声明。

修正后的初始化代码如下：

MyUI : slider_regular = slider_regular {
    DefaultValue := 100.0,
    DefaultMinValue := 0.0,
    DefaultMaxValue := 100.0,
    DefaultStepSize := 1.0
}

去掉所有属性后的:float类型标注，即可解决编译报错。

内容的提问来源于stack exchange，提问作者Brave.