Can you play guitar melodies by ear and if so how did you learn?!

Can you play guitar melodies by ear and if so how did you learn?

Also how long did it take to learn how to do it? And do you have any tips?

well when i started trying to learn guitar, i was horrible at everything!, but i loved it so i just kept playing and playing and now im good at it!

what i do is i hear the melody, like say for old mcdonald had a farm, "old mcdonald had a farm, ee ii ee ii oo:" and i sing it in my head over and over, then i take my guitar, and i just try to do on my guitar what im doing in my head, even if its wrong, i just play random notes, and try for like an hour to just get "old mcdonald had a farm" and also,
if you know the song, and you know how to read tabs, search in google somthing like "old mcdonald had a farm guitar tabs"
and then you will know what notes to hit, and then just make it sound like it does in your head. and you knw what they say, practice makes perfect, evertimg you play it or try to play it, you get a teeeensie bit better at it, so if you do it a hundred times, you will get a hundred teensie times better:D

and if you don't know how to read tabs, feel free to email me at johnwashburnx30@yahoo.com, or email me with any other guitar questions you might have.
cheers
good luck,
never quit!