Express the idea of "I was supposed"


I would like to know how to express "I was supposed" in japanese

For example, in the sentences :

[code]

    - Did you meet John yesterday ?
    - I was supposed to but he cancelled
    
[/code]

OR

[code]

    - I am supposed to do my homework but I really don't want to. 
    
[/code]

Is there a generic way to translate that idea ? or is it case by case ? I am
thinking maybe using ようになる but i am not really confident. somthing like :

[code]

    会ったようになったが、結局キャンセルされた、
    
[/code]

or using べき maybe

[code]

    宿題をやりべきだけど、やりたくない
    
[/code]

Am I on the right direction ?




I would say

昨日{きのう}Johnに会{あ}ったかい? for "Did you meet John yesterday?"

その筈{はず}だったけど、彼{かれ}にキャンセルされた for "I was supposed to but he cancelled."  
(彼が中止{ちゅうし}した, if you like non-transliterated words, but this sounds stilted.)

宿題をやらなければならないが、全然やりたくない for "I am supposed to do my homework but I really
don't want to."




I would say

昨日{きのう}Johnに会{あ}ったかい? for "Did you meet John yesterday?"

その筈{はず}だったけど、彼{かれ}にキャンセルされた for "I was supposed to but he cancelled."  
(彼が中止{ちゅうし}した, if you like non-transliterated words, but this sounds stilted.)

宿題をやらなければならないが、全然やりたくない for "I am supposed to do my homework but I really
don't want to."

