绑定。

D:\Projects\Program\Engine\Engine\Source\Runtime\UMG\Private\Components\CheckBox.cpp

MyCheckbox->SetIsChecked(OPTIONAL_BINDING(ECheckBoxState, CheckedState));

#define OPTIONAL_BINDING(ReturnType, MemberName)
\

( MemberName ## Delegate.IsBound() && !IsDesignTime() )
\

? \

TAttribute< ReturnType >::Create(MemberName ## Delegate.GetUObject(), MemberName ## Delegate.GetFunctionName()) \

: \

TAttribute< ReturnType >(MemberName)

OPTIONAL_BINDING返回一个ECheckBoxState，

MemberName ## Delegate.GetUObject() 等同于CheckedStateDelegate.GetUObject()，

CheckedStateDelegate是CheckBox的变量。