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OBJECTIVE-C class.Null is a generic pointer to a pointer of type C, null pointer to anything else. (#define NULL ((void *) 0))NSNull is a class in objective-c, used in situations where nil is not possible; A class defines a singleton object used to represent null values in collection Obje Cts(which don ' t allow nil values).[NSNull NULL]: The singleton instance of NSNull.[NSNull NULL] is an object that he uses in situations where nil can not be used.2. Memory leaks (the point of the stack is re

Lesson 3: Use ad Rotator)Parts The Internet web section is usually provided as an example. To make the festival interesting, and to show the advertisements of several customers in a limited space, you may also want to see different announcements through the loop. The ad rotator component simplifies the display of each advertising task in order, and makes the addition of new advertising work easier. In add

Regular expression classNSString *searchtext = @ "//do any additional setup after loading the view, typically from a nib.";Nserror *error = NULL;Nsregularexpression *regex = [Nsregularexpression regularexpressionwithpattern:@ "(?: [^,]) *\\." Options: Nsregularexpressioncaseinsensitive error:error];Nstextcheckingresult *result = [Regex firstmatchinstring:searchtext options:0 range:nsmakerange (0, [searchText length] )];if (result) {NSLog (@ "%@\n", [SearchText SubstringWithRange:result.range]);