Not quite.  

Gratian (1150-ish) tried to harmonize laws already extant at the time.  Catechesis has gone on, as the history of the name implies, for a significant portion of Christian history, though generally by the bishop or through his auspices.  The Roman Catechism was much influenced by Aquinas', developed almost 350 years earlier.

The benefit of having both a Code of Canon Law and a catechism is that most people can read them for themselves, now.  Just as, prior to John West's publishing of case law, the US legal system was difficult to navigate and precedent difficult to find, so the canons used in various jurisdictions across the world were difficult to reconcile.  The catechism, also, is not the sum of the Catholic faith; it is its summary.  Sufficient to answer a question about "what" the church teaches, but the "why" of that teaching requires significantly more diligence and study.