to show short action "as soon as he" + verb

一 is short for 一旦, which means once. 他一有=一旦他有

Dear exoriente 謝謝。That's what I wanted to say. :)

Sorry I can’t understand this sentence. Do y mean like “他一有时间就做某事”？ in sentence like this 一 means once.

Why do you need = 你为什么需要