swift - how to declare a generate protocol as delegate? -

we can make generate protocol follow:

protocol somedelegate {     typealias t     func xxx(x: t) } 

and make class conform it:

class aa: somedelegate {     typealias t = int     func xxx(x: t) {         // thing     } } 

and problem how declare propert conform generate protocol this:

class bb {     var delegate: somedelegate } 

the code on above raise error:

protocol 'somedelegate' can used generic constraint  because has self or associated type requirements  

it seems can use protocol delegate follow:

class bb {     var delegate: aa? } 

but, not want, cause delegate can't inherit other parent class

you use generics, using somedelegate type constraint:

class bb <u : somedelegate> {    var delegate: u? = nil } 

this way you'll need supply type of u when initialise instance of bb:

struct mystruct : somedelegate {     // argument of xxx needs concrete type here.     func xxx(x: int) {         // ...     } }  let bb = bb<mystruct>()