Objective-C implicit conversion loses integer precision NSUInteger aka unsigned long to int warning

Question

I m working through some exercises and have got a warning that states       Implicit conversion loses integer precision   NSUInteger   aka  unsigned long   to  int     import  lt Foundation Foundation h gt   int main  int argc  const char   argv           autoreleasepool            NSArray  myColors           int i          int count           myColors       Red     Green     Blue     Yellow             count   myColors count       lt  lt  lt  issue warning here          for  i   0  i  lt  count  i             NSLog    Element  i        i   myColors objectAtIndex  i               return 0

User · Accepted Answer

The count method of NSArray returns an NSUInteger  and on the 64-bit OS X platform   NSUInteger is defined as unsigned long  and unsigned long is a 64-bit unsigned integer  int is a 32-bit integer    So int is a  smaller  datatype than NSUInteger  therefore the compiler warning   See also NSUInteger in the  Foundation Data Types Reference       When building 32-bit applications  NSUInteger is a 32-bit unsigned   integer  A 64-bit application treats NSUInteger as a 64-bit unsigned   integer    To fix that compiler warning  you can either declare the local count variable as  NSUInteger count    or  if you are sure that your array will never contain more than 2 31-1 elements    add an explicit cast   int count    int  myColors count

User · Answer

Doing the expicit casting to the  int  solves the problem in my case  I had the same issue  So   int count    int  myColors count

User · Answer

Change key in Project   Build Setting  typecheck calls to printf scanf   NO   Explanation    How it works   Check calls to printf and scanf  etc   to make sure that the arguments supplied have types appropriate to the format string specified  and that the conversions specified in the format string make sense   Hope it work  Other warning   objective c implicit conversion loses integer precision  NSUInteger   aka  unsigned long   to  int  Change key   implicit conversion to 32Bits Type   Debug    64 architecture   No     caution  It may void other warning of 64 Bits architecture conversion

User · Answer

Contrary to Martin s answer  casting to int  or ignoring the warning  isn t always safe even if you know your array doesn t have more than 2 31-1 elements  Not when compiling for 64-bit   For example   NSArray  array       a     b     c     int i    int   array indexOfObject   d       indexOfObject returned NSNotFound  which is NSIntegerMax  which is LONG MAX in 64 bit     We cast this to int and got -1     But -1    NSNotFound  Trouble ahead   if  i    NSNotFound           thought we d get here  but we don t     NSLog   it s not here      else          this is what actually happens     NSLog   it s here   d   i                crash horribly          NSLog   the object is      array i

[objective-c] Objective-C implicit conversion loses integer precision 'NSUInteger' (aka 'unsigned long') to 'int' warning

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