What should be first - functionality or design? [duplicate]

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• How much design to do first? [duplicate] 4 answers

I've started reading a book from Head First series about OOP and Design. In a first chapter it is stated I have to worry about design of my application just after basic functionality is ready.

Basic functionality is ready means you have something to show to your customer or boss.

Do you think this is a correct approach? Shouldn't I think about design from the beginning? Can't it happen I won't have time for making a good design after functionality is ready because I will have new high priority requirements to implement?

By 'design' I mean Object Oriented design, not GUI or something.