Delphi Basics : copy command

DelphiBasics

copy
Function

Create a copy of part of a string or an array

System unit

1	function copy(Source string; StartChar, Count Integer):string;
2	function copy (Source array; StartIndex, Count Integer:array;

Description

The Copy function has 2 forms. In the first, it creates a new string from part of an existing string. In the second, it creates a new array from part of an existing array.

1.String copy

The first character of a string has index = 1.

Up to Count characters are copied from the StartChar of the Source string to the returned string.

Less than Count characters if the end of the Source string is encountered before Count characters have been copied.

2.Array copy

The first element of an array has index = 0.

Up to Count elements are copied from the StartIndex of the Source array to the returned array.

Less than Count elements if the end of the Source array is encountered before Count elements have been copied.

Notes

For string copying, a StartChar less than 1 is treated as 1.

To guarantee copying to the end of the string or array, use the MaxInt constant as the Count value.

When copying multi-dimensional arrays, only the first dimension is copied. The elements of all but the final dimension of an array are all pointers to sub-arrays that make up the whole array. After the copy, the target array elements continue to point to the sub-arrays of the source array. These sub-arrays are thereby shared by both the source and target arrays. You have been warned!

Related commands

AnsiReplaceStr		Replaces a part of one string with another
Concat		Concatenates one or more strings into one string
Delete		Delete a section of characters from a string
Insert		Insert a string into another string
Move		Copy bytes of data from a source to a destination
StringOfChar		Creates a string with one character repeated many times
StringReplace		Replace one or more substrings found within a string
StuffString		Replaces a part of one string with another
WrapText		Add line feeds into a string to simulate word wrap

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Example code : String copy

var
  Source, Target : string;

begin
  Source := '12345678';
  Target := Copy(Source, 3, 4);
  ShowMessage('Target : '+Target);
end;

Show full unit code

Target : 3456

Example code : Array copy

var
  i : Integer;
  Source, Target : array of Integer;

begin
  SetLength(Source, 8);

  for i := 1 to 8 do  // Build the dynamic source array
    Source[i-1] := i;  // Remember that arrays start at index 0

  Target := Copy(Source, 3, 4);

  for i := 0 to Length(Target) -1 do  // Display the created array
    ShowMessage('Target['+IntToStr(i)+'] : '+IntToStr(Target[i]));
end;

Show full unit code

  Target[0] : 4
  Target[1] : 5
  Target[2] : 6
  Target[3] : 7