Write the introduction first?

I’m working on the introduction chapter for “Begin to code: Building Apps and Games with the Cloud”. It was suggested that I should write the introduction when I’ve finished the entire text. That way I’ll know exactly what ended up in it. I quite like this idea, but I think I’ll try and write the introduction first. I think it is better to have an idea where you are going before you start. And I can always revise it later…