Delphi检查字符是否在'A'..'Z'和'0'..'9'范围内 [英] Delphi check if character is in range 'A'..'Z' and '0'..'9'
问题描述
我需要检查字符串是否仅包含范围内的字符:'A'..'Z', 'a'..'z', '0'..'9'
,所以我编写了此函数:
I need to check if a string contains only characters from ranges: 'A'..'Z', 'a'..'z', '0'..'9'
, so I wrote this function:
function GetValueTrat(aValue: string): string;
const
number = [0 .. 9];
const
letter = ['a' .. 'z', 'A' .. 'Z'];
var
i: Integer;
begin
for i := 1 to length(aValue) do
begin
if (not(StrToInt(aValue[i]) in number)) or (not(aValue[i] in letter)) then
raise Exception.Create('Non valido');
end;
Result := aValue.Trim;
end;
但是例如,如果aValue = 'Hello'
StrToInt
函数引发异常.
but if for example, aValue = 'Hello'
the StrToInt
function raise me an Exception.
推荐答案
一组独特的Char
可用于您的目的.
An unique set of Char
can be used for your purpose.
function GetValueTrat(const aValue: string): string;
const
CHARS = ['0'..'9', 'a'..'z', 'A'..'Z'];
var
i: Integer;
begin
Result := aValue.Trim;
for i := 1 to Length(Result) do
begin
if not (Result[i] in CHARS) then
raise Exception.Create('Non valido');
end;
end;
请注意,在函数中,如果aValue
包含空格字符(例如'test value '
),则会引发异常,因此在if
语句后使用Trim
是无用的.
Notice that in your function if aValue
contains a space character - like 'test value '
for example - an exception is raised so the usage of Trim
is useless after the if
statement.
在我看来,像^[0-9a-zA-Z]
这样的正则表达式可以更优雅地解决您的问题.
A regular expression like ^[0-9a-zA-Z]
can solve your issue in a more elegant way in my opinion.
编辑
根据 @RBA的评论一个问题, System.Character.TCharHelper.IsLetterOrDigit 可以替代上述逻辑:
EDIT
According to the @RBA's comment to the question, System.Character.TCharHelper.IsLetterOrDigit can be used as a replacement for the above logic:
if not Result[i].IsLetterOrDigit then
raise Exception.Create('Non valido');
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