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RandomFrom

Function RandomFrom( const AValues : TStringArray) : string

Example​

procedure ScriptEvent(var Value: variant);
var
  Choices: TStringArray;
begin
  SetArrayLength(Choices, 3);
  Choices[0] := 'Queued';
  Choices[1] := 'Ready';
  Choices[2] := 'Held';
  Value := RandomFrom(Choices);
end;

Usage​

RandomFrom returns one element selected by Velox's process-wide pseudo-random generator from a non-empty string array.

Parameters

ParameterTypeMeaning
AValuesTStringArrayNon-empty array of candidate strings. Duplicate values are separate positions and therefore increase that value's selection probability.

Return value

The element at Random(Length(AValues)). The array is not modified.

Important behavior and quirks

  • The array must contain at least one element. Empty input still computes index zero and then indexes an empty array; depending on runtime checking this can raise a range error or access invalid data. Treat it as invalid input.
  • Empty strings are valid array elements and may be returned.
  • Selection is by array position, not by distinct value.
  • The result is not stable unless the generator seed and the complete sequence of all intervening random calls are controlled.
  • Velox does not initialise or isolate a private generator for this call. Other code using Velox Random, Randomize or RandSeed affects the sequence.

Security and concurrency

The generator is predictable and unsuitable for passwords, tokens, identifiers, cryptographic keys, security decisions or unbiased regulated draws. Its shared seed is mutated without a per-call lock, so concurrent calls can race and make sequence reproduction unreliable.

Additional Technical Info​

RandomFrom returns one string from AValues. Every valid array position is selected through Delphi's standard pseudo-random number generator.

The example is fictional and source-reviewed only. Its output is intentionally nondeterministic.

How it works

The StrUtils implementation evaluates AValues[Random(High(AValues) + 1)]. In the installed Delphi runtime, Random(Integer) advances a global linear-congruential generator and scales its 32-bit output into the requested range.

Errors and limits

Apart from empty input, a very large array is limited by the script array and signed integer range. Returning an element copies or shares the managed string according to Delphi string semantics.

External references

Created 2026-07-15