vault backup: 2024-10-12 17:19:45

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/String/AllowedCharacters/AllowedCharacters.md

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+# AllowedCharacters
+
+- **功能描述：** 只允许文本框里可以输入这些字符。
+- **使用位置：** UPROPERTY
+- **引擎模块：** String/Text Property
+- **元数据类型：** string="abc"
+- **限制类型：** FName/FString/Fext
+- **常用程度：** ★★★
+
+只允许文本框里可以输入这些字符。
+
+## 测试代码：
+
+```cpp
+public:
+	UPROPERTY(EditAnywhere, Category = AllowedCharactersTest, meta = (AllowedCharacters = "abcde"))
+	FString MyString_AllowedCharacters;
+	UPROPERTY(EditAnywhere, Category = AllowedCharactersTest, meta = (AllowedCharacters = "你好"))
+	FString MyString_AllowedCharacters_Chinese;
+```
+
+## 测试效果：
+
+可见第一个只能输入abcde，而fgh产生了报错。在测试中文的时候，如果粘贴进去对应的中文，则是OK的。否则也会产生报错，不允许输入进去。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+SPropertyEditorText里实际保存了FCharRangeList 的AllowedCharacters用来限制字符。同样在字符串改变的时候，验证字符是否合法。
+
+```cpp
+
+FCharRangeList AllowedCharacters;
+
+AllowedCharacters.InitializeFromString(PropertyHandle->GetMetaData(NAME_AllowedCharacters));
+
+bool SPropertyEditorText::OnVerifyTextChanged(const FText& Text, FText& OutError)
+{
+	const FString& TextString = Text.ToString();
+
+	if (MaxLength > 0 && TextString.Len() > MaxLength)
+	{
+		OutError = FText::Format(LOCTEXT("PropertyTextTooLongError", "This value is too long ({0}/{1} characters)"), TextString.Len(), MaxLength);
+		return false;
+	}
+
+	if (!AllowedCharacters.IsEmpty())
+	{
+		if (!TextString.IsEmpty() && !AllowedCharacters.AreAllCharsIncluded(TextString))
+		{
+			TSet<TCHAR> InvalidCharacters = AllowedCharacters.FindCharsNotIncluded(TextString);
+			FString InvalidCharactersString;
+			for (TCHAR Char : InvalidCharacters)
+			{
+				if (!InvalidCharactersString.IsEmpty())
+				{
+					InvalidCharactersString.AppendChar(TEXT(' '));
+				}
+				InvalidCharactersString.AppendChar(Char);
+			}
+			OutError = FText::Format(LOCTEXT("PropertyTextCharactersNotAllowedError", "The value may not contain the following characters: {0}"), FText::FromString(InvalidCharactersString));
+			return false;
+		}
+	}
+
+	if (PropertyValidatorFunc.IsBound())
+	{
+		FText Result = PropertyValidatorFunc.Execute(TextString); 
+		if (!Result.IsEmpty())
+		{
+			OutError = Result;
+			return false;
+		}
+	}
+
+	return true;
+}
+```
+
+根据FCharRangeList的定义，限制字符的格式是：
+
+```cpp
+/** Initializes this instance with the character ranges represented by the passed definition string.
+*   A definition string contains characters and ranges of characters, one after another with no special separators between them.
+*   Characters - and \ must be escaped like this: \- and \\
+* 
+*   Examples:
+*       "aT._" <-- Letters 'a' and 'T', dot and underscore.
+*       "a-zT._" <-- All letters from 'a' to 'z', letter 'T', dot and underscore.
+*       "a-zA-Z0-9._" <-- All lowercase and uppercase letters, all digits, dot and underscore.
+*       "a-zA-Z0-9\-\\._" <-- All lowercase and uppercase letters, all digits, minus sign, backslash, dot and underscore.
+*/
+```