If your idea is in early days and you are still in the research process, there are a few ways to share it with potential developers without exposing yourself to too much risk.

Nondisclosure Agreement (NDA) - a legal document that both parties sign to acknowledge that the project discussed is not to be shared with anyone outside the project without permission.
Use comparable examples - when describing an idea to a programmer or engineer, explain it with something comparable.
Break it up - Discuss only parts of the idea with certain people. Don't expose your secret weapon. For example, discuss the technical parts, but don't tell how you are planning to monetize it.
There is no real, bulletproof way to stop someone from stealing your idea. Instead of focusing on protecting it, you should focus on executing it.