Author: Ernesto De Spirito

A function that splits a string in parts separated by a substring and returns the 
parts in a StringList

Answer:

Solve 1:

The following functions split a string in parts separated by a substring and return 
the parts in a string list that may be passed as third parameter or created by the 
function (and in this latter case it must be freed by the caller): 

1   interface
2   
3   uses classes;
4   
5   function SplitStrings(const str: string;
6     const separator: string = ',';
7     Strings: TStrings = nil): TStrings;
8   function AnsiSplitStrings(const str: string;
9     const separator: string = ',';
10    Strings: TStrings = nil): TStrings;
11  
12  implementation
13  
14  uses sysutils;
15  
16  function SplitStrings(const str: string; const separator: string;
17    Strings: TStrings): TStrings;
18  // Fills a string list with the parts of "str" separated by
19  // "separator". If Nil is passed instead of a string list,
20  // the function creates a TStringList object which has to
21  // be freed by the caller
22  var
23    n: integer;
24    p, q, s: PChar;
25    item: string;
26  begin
27    if Strings = nil then
28      Result := TStringList.Create
29    else
30      Result := Strings;
31    try
32      p := PChar(str);
33      s := PChar(separator);
34      n := Length(separator);
35      repeat
36        q := StrPos(p, s);
37        if q = nil then
38          q := StrScan(p, #0);
39        SetString(item, p, q - p);
40        Result.Add(item);
41        p := q + n;
42      until q^ = #0;
43    except
44      item := '';
45      if Strings = nil then
46        Result.Free;
47      raise;
48    end;
49  end;
50  
51  function AnsiSplitStrings(const str: string; const separator: string;
52    Strings: TStrings): TStrings;
53  // Fills a string list with the parts of "str" separated by
54  // "separator". If Nil is passed instead of a string list,
55  // the function creates a TStringList object which has to
56  // be freed by the caller
57  // ANSI version
58  var
59    n: integer;
60    p, q, s: PChar;
61    item: string;
62  begin
63    if Strings = nil then
64      Result := TStringList.Create
65    else
66      Result := Strings;
67    try
68      p := PChar(str);
69      s := PChar(separator);
70      n := Length(separator);
71      repeat
72        q := AnsiStrPos(p, s);
73        if q = nil then
74          q := AnsiStrScan(p, #0);
75        SetString(item, p, q - p);
76        Result.Add(item);
77        p := q + n;
78      until q^ = #0;
79    except
80      item := '';
81      if Strings = nil then
82        Result.Free;
83      raise;
84    end;
85  end;


Examples: 

86  procedure TForm1.Button1Click(Sender: TObject);
87  begin
88    SplitStrings(Edit1.Text, ', ', ListBox1.Items);
89  end;
90  
91  procedure TForm1.Button2Click(Sender: TObject);
92  var
93    Parts: TStrings;
94  begin
95    Parts := nil;
96    try
97      Parts := SplitStrings(Edit1.Text, ', ');
98      ShowMessage('First part is "' + Parts[0] + '"');
99    finally
100     Parts.Free;
101   end;
102 end;


You can see an example using a dynamic array instead of a StringList in a separate 
article "Splitting a string in an dynamic arraydkb://531023430".


Solve 2:

Shorten way: 

103 function SplitStrings(const str: string; const separator: string;
104   Strings: TStrings): TStrings;
105 // Fills a string list with the parts of "str" separated by
106 // "separator". If Nil is passed instead of a string list,
107 // the function creates a TStringList object which has to
108 // be freed by the caller
109 begin
110   if Strings = nil then
111     Result := TStringList.Create
112   else
113     Result := Strings;
114 
115   //This replaces the separators in str with CRLF so as to fit the format  of a 
116 stringlist.
117   Result.Text := StringReplace(str, separator, #13#10, [rfReplaceAll]);
118 end;