不要忘记 引入 这个单元，System.SysUtils 否则报错，什么也点不出来；
大小写转换
function ToLower: string;
function ToLower(LocaleID: TLocaleID): string;
function ToLowerInvariant: string;
function ToUpper: string;
function ToUpper(LocaleID: TLocaleID): string;
function ToUpperInvariant: string;
class function LowerCase(const S: string): string;
class function LowerCase(const S: string; LocaleOptions: TLocaleOptions): string;
class function UpperCase(const S: string): string;
class function UpperCase(const S: string; LocaleOptions: TLocaleOptions): string;
//--------------------------------------------------------------------------------
var
str: string;
begin
str := 'Delphi';
str := str.ToLower; // delphi
str := str.ToUpper; // DELPHI
end;
清除两边空格或指定字符
function Trim: string;
function TrimLeft: string;
function TrimRight: string;
function Trim(const TrimChars: array of Char): string;
function TrimLeft(const TrimChars: array of Char): string;
function TrimRight(const TrimChars: array of Char): string;
//--------------------------------------------------------------------------------
var
str1, str2: string;
begin
str1 := ' Delphi 10000 ';
str2 := str1.TrimLeft; // 'Delphi 10000 '
str2 := str1.TrimRight; // ' Delphi 10000'
str2 := str1.Trim; // 'Delphi 10000'
str2 := str1.Trim([' ', '0']); // 'Delphi 1'
end;
字符串对比
function CompareTo(const strB: string): Integer;
class function Compare(const StrA: string; const StrB: string): Integer;
class function CompareText(const StrA: string; const StrB: string): Integer;
class function Compare(const StrA: string; const StrB: string; LocaleID: TLocaleID): Integer;
class function Compare(const StrA: string; const StrB: string; IgnoreCase: Boolean): Integer;
class function Compare(const StrA: string; const StrB: string; IgnoreCase: Boolean; LocaleID: TLocaleID): Integer;
class function Compare(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer): Integer;
class function Compare(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer; LocaleID: TLocaleID): Integer;
class function Compare(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer; IgnoreCase: Boolean): Integer;
class function Compare(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer; IgnoreCase: Boolean; LocaleID: TLocaleID): Integer;
class function CompareOrdinal(const StrA: string; const StrB: string): Integer;
class function CompareOrdinal(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer): Integer;
//--------------------------------------------------------------------------------
var
str1, str2: string;
n: Integer;
begin
str1 := 'ABC 123';
str2 := 'abc 123';
n := str1.CompareTo(str2); // -32
n := str1.Compare(str1, str2); // 1
n := str1.CompareText(str1, str2); // 0; 相同
n := str1.Compare(str1, str2, True); // 0; 不区分大小写
n := str1.CompareOrdinal(str1, str2); // -32
n := str1.Compare(str1, 4, str2, 4, 3); // 0; 只对比后三位
end;
搜索字符串
function IndexOf(value: Char): Integer;
function IndexOf(const Value: string): Integer;
function IndexOf(Value: Char; StartIndex: Integer): Integer;
function IndexOf(const Value: string; StartIndex: Integer): Integer;
function IndexOf(Value: Char; StartIndex: Integer; Count: Integer): Integer;
function IndexOf(const Value: string; StartIndex: Integer; Count: Integer): Integer;
function IndexOfAny(const AnyOf: array of Char): Integer;
function IndexOfAny(const AnyOf: array of Char; StartIndex: Integer): Integer;
function IndexOfAny(const AnyOf: array of Char; StartIndex: Integer; Count: Integer): Integer;
function LastIndexOf(Value: Char): Integer;
function LastIndexOf(const Value: string): Integer;
function LastIndexOf(Value: Char; StartIndex: Integer): Integer;
function LastIndexOf(const Value: string; StartIndex: Integer): Integer;
function LastIndexOf(Value: Char; StartIndex: Integer; Count: Integer): Integer;
function LastIndexOf(const Value: string; StartIndex: Integer; Count: Integer): Integer;
function LastIndexOfAny(const AnyOf: array of Char): Integer;
function LastIndexOfAny(const AnyOf: array of Char; StartIndex: Integer): Integer;
function LastIndexOfAny(const AnyOf: array of Char; StartIndex: Integer; Count: Integer): Integer;
//--------------------------------------------------------------------------------
var
str: string;
n: Integer;
begin
str := 'A1 A2 A3 A4';
n := str.IndexOf('A'); // 0
n := str.LastIndexOf('A'); // 9
n := str.IndexOf('B'); // -1; 没找到
n := str.IndexOf('A', 1, str.Length - 1); // 3
n := str.LastIndexOf('A', str.Length - 1, str.Length - 1); // 9
n := str.IndexOfAny(['1', '2', '3', '4']); // 1
n := str.LastIndexOfAny(['1', '2', '3', '4']); // 10
end;
是否包含
function Contains(const Value: string): Boolean;
function StartsWith(const Value: string): Boolean;
function StartsWith(const Value: string; IgnoreCase: Boolean): Boolean;
function EndsWith(const Value: string): Boolean;
function EndsWith(const Value: string; IgnoreCase: Boolean): Boolean;
class function EndsText(const ASubText, AText: string): Boolean;
//--------------------------------------------------------------------------------
var
str: string;
b: Boolean;
begin
str := 'Delphi XE4';
b := str.Contains('XE'); // True
b := str.Contains('xe'); // False
b := str.StartsWith('delphi'); // False
b := str.StartsWith('delphi', True); // True
b := str.EndsWith('XE4'); // True
b := str.EndsText('xe4', str); // True
end;
添加或解除引号
function QuotedString: string;
function QuotedString(const QuoteChar: Char): string;
function DeQuotedString: string;
function DeQuotedString(const QuoteChar: Char): string;
//--------------------------------------------------------------------------------
var
str1, str2: string;
begin
str1 := 'Delphi';
str2 := str1.QuotedString; // 'Delphi'
str2 := str1.QuotedString('"'); // "Delphi"
str1 := '"Delphi"';
str2 := str1.DeQuotedString('"'); // Delphi
end;
适宽处理
function PadLeft(TotalWidth: Integer): string;
function PadLeft(TotalWidth: Integer; PaddingChar: Char): string;
function PadRight(TotalWidth: Integer): string;
function PadRight(TotalWidth: Integer; PaddingChar: Char): string;
//--------------------------------------------------------------------------------
var
str: string;
begin
str := '1';
str := str.PadLeft(4, '0'); // 0001
end;
插入与删除（startIndex是从0开始）
function Insert(StartIndex: Integer; const Value: string): string;
function Remove(StartIndex: Integer): string;
function Remove(StartIndex: Integer; Count: Integer): string;
//--------------------------------------------------------------------------------
var
str1, str2: string;
begin
str1 := 'Delphi 4';
str2 := str1.Insert(7, 'XE'); // Delphi XE4
str1 := 'Delphi XE4';
str2 := str1.Remove(6); // Delphi
str2 := str1.Remove(7, 2); // Delphi 4
end;
str[index] 这个index是从1开始的，而Insert、Remove、SubString都是从0开始的，切记，看下面的截取说明！！！！
截取（startIndex是从0开始）
function Substring(StartIndex: Integer): string;
function Substring(StartIndex: Integer; Length: Integer): string;
//--------------------------------------------------------------------------------
var
str1, str2: string;
begin
str1 := 'Delphi XE4';
str2 := str1.Substring(7); // XE4
str2 := str1.Substring(7, 2); // XE
end;
//--------------------------------------------------------------------------------
procedure TForm3.btn1Click(Sender: TObject);
var
s: string;
begin
s := '123456';
mmo1.Lines.Add(s[1]); //1，下标从1开始
mmo1.Lines.Add(s.Substring(1, 1)); //2，下标从0开始
end;
//这也是一个常见用法
procedure TForm12.btn1Click(Sender: TObject);
var
wokao: string;
begin
wokao := 'abcde_fg';
ShowMessage(IntToStr(wokao.IndexOf('_')));//5
ShowMessage(wokao.Substring(0,wokao.IndexOf('_')));//abcde
end;
//========================== 最常用的用法，根据ps来截取 ========================
procedure TForm2.btn1Click(Sender: TObject);
begin
var json := '12345';
var ps := 1;
var startPs := ps;
repeat
Inc(ps);
until json[ps] = '5';
var content := json.Substring(startPs - 1, ps - startPs); // 1234
//json.Substring(startPs - 1 : Substring是索引从0开始的，故而减去1
//ps - startPs 表示差值，拷贝几个字符，从第一个字符开始，不包含最后一个5；即：1 - 4
// ps - startPs 的意思是，从第一个字符 ---> 当前光标前的一个字符；当前光标在5，所以是 1 - 4；
end;
上面截取的用法，最常用，要记着 2 要素，startPs - 1 和 ps - startPs ；以后就这样用就可以了，不用每次都推导；
替换
function Replace(OldChar: Char; NewChar: Char): string;
function Replace(OldChar: Char; NewChar: Char; ReplaceFlags: TReplaceFlags): string;
function Replace(const OldValue: string; const NewValue: string): string;
function Replace(const OldValue: string; const NewValue: string; ReplaceFlags: TReplaceFlags): string;
//--------------------------------------------------------------------------------
var
str1, str2: string;
begin
str1 := 'ABC ABC ABC';
str2 := str1.Replace('A', '*'); // *BC *BC *BC
str2 := str1.Replace('A', '*', [rfIgnoreCase]); // *BC ABC ABC
end;
分割
function Split(const Separator: array of Char): TArray<string>;
function Split(const Separator: array of Char; Count: Integer): TArray<string>;
function Split(const Separator: array of Char; Options: TStringSplitOptions): TArray<string>;
function Split(const Separator: array of string; Options: TStringSplitOptions): TArray<string>;
function Split(const Separator: array of Char; Count: Integer; Options: TStringSplitOptions): TArray<string>;
function Split(const Separator: array of string; Count: Integer; Options: TStringSplitOptions): TArray<string>;
//--------------------------------------------------------------------------------
var
str: string;
arr: TArray<string>;
begin
str := 'A-1,B-2,,,C-3,D-4';
arr := str.Split([',']); // arr[0] = A-1; Length(arr) = 6
arr := str.Split([','], TStringSplitOptions.ExcludeEmpty); // 忽略空项; Length(arr) = 4
arr := str.Split([','], 2); // 只提取前 2
arr := str.Split([',', '-'], ExcludeEmpty); //arr[0] = A; Length(arr) = 8
arr := str.Split([',,,'], None); // 分隔符可以是一个字符串数组
end;
//--------------------------------------------------------------------------------
procedure TForm2.btn1Click(Sender: TObject);
var
str1, str2, str3: string;
s: string;
begin
mmo1.Lines.Clear;
str1 := ''; //空被分隔后，一定是空数组
for s in str1.Split([',']) do
begin
mmo1.Lines.Add(s); //这里不会有任何输出
end;
str2 := 'a'; //一个元素被分隔的话，会分隔出来一个元素
for s in str2.Split([',']) do
begin
mmo1.Lines.Add(s); //a
end;
str3 := ','; //会被分隔成左右两个空元素
var flag := 0;
for s in str3.Split([',']) do
begin
mmo1.Lines.Add(flag.ToString + s);
Inc(flag);
end;
end;
//输出：
a
0
1
连接
class function Join(const Separator: string; const values: array of const): string;
class function Join(const Separator: string; const Values: array of string): string;
class function Join(const Separator: string; const Values: IEnumerator<string>): string;
class function Join(const Separator: string; const Values: IEnumerable<string>): string;
class function Join(const Separator: string; const value: array of string; StartIndex: Integer; Count: Integer): string;
//--------------------------------------------------------------------------------
var
S: string;
str: string;
strArr: TArray<string>;
begin
str := 'A1,B2,C3,,,,D4,E5,F6,G7';
strArr := str.Split([','], ExcludeEmpty);
str := S.Join('-', strArr); // A1-B2-C3-D4-E5-F6-G7
str := S.Join('; ', [1,2,3,4,5]); // 1; 2; 3; 4; 5
str := S.Join(',', ['abc', 123, true]); // abc,123,True
end;
类型转换
function ToBoolean: Boolean;
function ToInteger: Integer;
function ToSingle: Single;
function ToDouble: Double;
function ToExtended: Extended;
class function ToBoolean(const S: string): Boolean;
class function ToInteger(const S: string): Integer;
class function ToSingle(const S: string): Single;
class function ToDouble(const S: string): Double;
class function ToExtended(const S: string): Extended;
class function Parse(const Value: Integer): string;
class function Parse(const Value: Int64): string;
class function Parse(const Value: Boolean): string;
class function Parse(const Value: Extended): string;
//--------------------------------------------------------------------------------
var
S: string;
str: string;
n: Integer;
b: Boolean;
f: Double;
begin
str := S.Parse(123);
n := str.ToInteger; // 123
b := str.ToBoolean; // True
str := S.Parse(True);
b := str.ToBoolean; // True
n := str.ToInteger; // -1
str := S.Parse(3.14159260000);
f := str.ToDouble; //3.1415926
end;
定界符
function IsDelimiter(const Delimiters: string; Index: Integer): Boolean;
function LastDelimiter(const Delims: string): Integer;
//--------------------------------------------------------------------------------
var
str: string;
b: Boolean;
n: Integer;
begin
str := 'http://del.cnblogs.com';
b := str.IsDelimiter(':', 4); // True
b := str.IsDelimiter('//', 5); // True
n := str.LastDelimiter('.'); // 18
n := str.IndexOf('.'); // 10
end;
空字符串
const Empty = '';
function IsEmpty: Boolean;
class function IsNullOrEmpty(const Value: string): Boolean;
class function IsNullOrWhiteSpace(const Value: string): Boolean;
//--------------------------------------------------------------------------------
var
S: string;
str: string;
b: Boolean;
begin
str := ' ';
b := str.IsEmpty; // False
b := S.IsNullOrWhiteSpace(str); // True
end;
String 与 Char
class function Create(C: Char; Count: Integer): string;
class function Create(const Value: array of Char; StartIndex: Integer; Length: Integer): string;
class function Create(const Value: array of Char): string;
property Chars[Index: Integer]: Char read GetChars;
property Length: Integer read GetLength;
function CountChar(const C: Char): Integer;
function ToCharArray: TArray<Char>;
function ToCharArray(StartIndex: Integer; Length: Integer): TArray<Char>;
procedure CopyTo(SourceIndex: Integer; var destination: array of Char; DestinationIndex: Integer; Count: Integer);
//--------------------------------------------------------------------------------
var
S: string;
str, str2: string;
charArr: TCharArray;
n: Integer;
c: Char;
begin
str := 'ABC';
n := str.Length; // 3
c := str.Chars[0]; // A = str[1]
str := S.Create('A', 7); // AAAAAAA
charArr := 'ABCDEFG'.ToCharArray;
str := s.Create(charArr); // ABCDEFG
str := S.Create(charArr, 1, 3); // BCD
charArr := '1234567890'.ToCharArray;
str := 'ABCDEFG';
str.CopyTo(1, charArr, 2, 3);
str := S.Create(charArr); // 12BCD67890
end;
其他
function Equals(const Value: string): Boolean;
function GetHashCode: Integer;
class function Equals(const a: string; const b: string): Boolean;
class function Format(const Format: string; const args: array of const): string;
class function Copy(const Str: string): string;
本文来自博客园，作者：del88，转载请注明原文链接：https://www.cnblogs.com/del88/p/18066347
