Article 223 of Civil Code

1 - Revocation of the promise of a reward shall have effect only from the date it is announced to the public, and shall not affect the right to the reward of anyone who has completed the work in good faith before that time. 2 - If no one has completed the work, a person who began the work in good faith before the announcement of the revocation of the promise, without completing it, may claim from the promisor, within the limit of the reward, the value of his expenditure and effort, if he proves that he would have completed the work within a suitable time.