ios - Objective-C: self = nil doesn't set instance to null value -

i've got next code, pretty simple:

//secondviewcontroller.m if(contentrvcontroller==nil){     contentrvcontroller = [[contentview alloc]      initwithnibname:@"contentview" bundle:nil]; //contentview custom uiviewcontroller     ....     [self.view addsubview:contentrvcontroller.view]; } else{     contentrvcontroller.view.hide = yes;     [contentrvcontroller release];     contentrvcontroller = nil; } 

basically, when code launched button, if uiviewcontroller not exist, create 1 , display (it meant displayed on main bigger desktop view, secondviewcontroller view). if opened, close , remove free resources.

now, contentrvcontroller instance of contentview, custom uiviewcontroller. has it's own close uibutton ibaction this:

//contentview.m - (ibaction) closeview {     self.view.hidden = yes;     [self release];     self = nil; } 

now, when triggered secondviewcontroller, releasing contentrvcontroller works (or seems me), view appears , disappears. when contentview close button tapped closes view, when trying open again if(contentrvcontroller==nil) returns false, have tap twice button execute in order display again contentview.

it seems me self = nil; works different contentrvcontroller = nil; although supposed both points same place, , im lost this.

¿any idea? cheers méxico

they work same way, they're not doing think do. = not affect object; affects variable pointing object. setting 1 variable point nil won't change value of other variables in program. similarly:

int = 5; int b = a; b = 6; printf("a %d , b %d\n", a, b); 

this print "a 5 , b 6" — because setting b new value doesn't change value of a.