Create a constant array of strings

Question

Is there a way in Delphi declaring an array of strings such as following one?

{'first','second','third'}

Solution 1

try this

Const
Elements =3;
MyArray  : array  [1..Elements] of string = ('element 1','element 2','element 3');

Solution 2

In XE7 you can declare a dynamic array constant like this:

const
  MyArray: TArray<String> = ['First','Second','Third'];

Solution 3

You can use dynamic arrays and try this:

var
  FMyArray: TArray<string>;

function MyArray: TArray<string>;
begin
  if Length(FMyArray) = 0 then
    FMyArray := TArray<string>.Create('One', 'Two', 'Three');
  Result := FMyArray;
end;

While this does do a run-time initialization of a dynamic array on the heap, it also shows that Delphi supports a "pseudo-constructor" on dynamic arrays that allow in-place initialization. (NOTE: the above code isn't thread-safe).

Now all you need to do to find out the length of the array, is use the Length() standard function, or to find the allowed index range, use the Low() and High() standard functions.

If you're using an older version of Delphi, replace the TArray with your own dynamic-array string type such as:

type
  TStringArray = array of string;

Solution 4

You can do this in a indirect way. Create a function like:

procedure assignStringArray(var rasVelden: ArrayOfString; const asVeldenIn: Array Of String);
var
   iLengte, iT1: Integer;
begin
   iLengte := Length(asVeldenIn);
   SetLength(rasVelden, iLengte);
   for iT1 := iLengte-1 downto 0 do
      rasVelden[iT1] := asVeldenIn[iT1];
end;

and call this function like:

assignStringArray(asVelden, ['String1', 'String2', 'String3']);

where:

asVelden: ArrayOfString; 

View more solutions

Comments

[none]

thanks, thow i was hopping to avoid the use of Elements and let the Delphi calculate the size of the array.

[none]

true, that is valid, however it needs to be const and not runtime.

[Admin]

You can avoid the Elements constant, but you have to declare the array size anyway. You can use the "short form" array[x] where x is an enumerated type, creating an array from the first to the last element of the type. The compiler does not support array[] = (1,2,3) calculating the array size and setting a 0..2 boundary automatically.

[Allen Bauer]

The elements are constant, only the array is not. Other than a startup cost, there is very little runtime overhead. Does it need to be const merely because of tradition or is there something specific to your case that requires const?

[none]

if the array is not const then the array could change. does not fit requirements. the idea is nice tho.

[crazy_in_love]

This is a nifty feature. Almost make me want to upgrade!

[Jerry Dodge]

Brilliant, all this time I thought this wasn't possible :D

[drakorg]

This saved my day. Thanks.

[tmjac2]

I love this. It allows you to do a forin loop (for S in MyArray do)

[Marcus Mangelsdorf]

Please note that due to the compiler bug documented in RSP-21151 this currently doesn't work for class constants (fails with E2086 Type 'TArray<T>' is not yet completely defined), unless you add an additional: type TStringArray = TArray<string>; to your unit. | (Note that it must be in a separate type section to prevent the bug and that the workaround doesn't seem to work for generic classes. See the ticket for all details.)

[Wolf]

It is indispensable to see such an array literal in action.