iphone - When to use a colon with a @selector -

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just getting going iphone development , objective-c.

yesterday trying addobserver notification in view of mine, , kept getting error:

unrecognized selector sent instance

i tracked down fact needed include trailing colon selector argument:

[[nsnotificationcenter defaultcenter] addobserver:self selector:@selector(nameofmyselector:) name:@"bblocationservicesaredisabled" object:nil];

today, thought clever because when setting action argument button, remembered mistake yesterday, , added colon action argument. action argument takes @selector, selector argument while setting observer nsnotification, figured doing right thing.

however, following code:

[self.calltoactionbutton addtarget:self action:@selector(nameofmyselector:) forcontrolevents:uicontroleventtouchupinside];

i exact same error:

unrecognized selector sent instance

what gives? why 1 @selector require trailing colon, , other doesn't? rules should follow when should included , when should left off, , why can't 1 or other?

thanks!

as mentioned boltclock, character referring colon. difference between @selector(method) , @selector(method:) method signature. 2nd variant expects parameter passed.

@selector(method) expect method: -(void)method

@selector(method:) expect method: -(void)method:(id)someparameter


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