"Learning the path of iOS: Objective-c" The system ordering method commonly used in OC

Common sorting methods in ①.oc:

1). Non-variable group

-(Nsarray *) Sortedarrayusingselector: (SEL) comparator;-(Nsarray *) Sortedarrayusingcomparator: (NSComparator) cmptr;

2) Variable Group

-(void) Sortusingselector: (SEL) comparator;-(void) Sortusingcomparator: (Nscomparator) cmptr;

3). Dictionary sort

-(Nsarray *) Keyssortedbyvalueusingcomparator: (Nscomparator) Cmptr-(Nsarray *) Keyssortedbyvalueusingselector: (SEL) Comparator

② Applications

1). Array of Immutable Variables: (Method 1)

   Nsarray *arr = @[@ "AA", @ "RR", @ "pp", @ "hh", @ "xx", @ "VV"];   The system lacks the method of two element comparison to sort by the system method.   The Selector method selector.        Nsarray *sortarr = [arr sortedarrayusingselector: @selector (compare:)];    NSLog (@ "%@", Sortarr);   

Method 2:block Block syntax

   [Arr sortedarrayusingcomparator:^nscomparisonresult (ID obj1, id obj2) {        return [(NSString *) obj1 compare: (nsstring *) obj2];    }];     NSLog (@ "%@", arr);    }

2). Variable Array Ordering: Method 1

    Nsmutablearray *arr = [@[@54, @33,@12,@23,@65] mutablecopy];    [Arr sortusingselector: @selector (Compare:) method    for comparing two elements in an array];//compare NSLog (@ "%@", arr);

Method 2

   [Arr sortusingcomparator:^nscomparisonresult (ID obj1, id obj2) {        return [(NSNumber *) obj1 Compare: (NSNumber *) obj2 ];    }];     NSLog (@ "%@", arr);    }

Note: The dictionary method is similar

③. Example: Define a Student object, according to the student object, name, age, score, number of students to sort, (two sorts of ways)

Method 1: (with the Selector method selector, you need to redefine the comparator)

The code is as follows:

1. Object declaration (in student.h)

@property (nonatomic, retain) nsstring *name; @property (nonatomic, assign) Nsinteger age; @property (nonatomic, assign) CG Float score; @property (nonatomic, assign) Nsinteger number;//initialization-(ID) Initwithname: (NSString *) name Age: (Nsinteger) Age Score:                                  (cgfloat) score number: (Nsinteger) number;//convenience Builder + (ID) studentwithname: (NSString *) name Age: (Nsinteger) Age Score:                                   (cgfloat) score number: (Nsinteger) number;//Two students according to the method of comparison-(Nscomparisonresult) Comparebyage: (Student *) stu;//two students by name comparison Method-(Nscomparisonresult) Comparebyname: (Student *) stu;//two students according to the method of comparison-(Nscomparisonresult) Comparebyscore: (Student *) stu;//two students in accordance with the method of the number comparison-(Nscomparisonresult) Comparebynumber: (Student *) Stu;

2. Implementation (STUDENT.M file)

 -(ID) Initwithname: (NSString *) Name: (Nsinteger) Age Score: (cgfloat) score Numbe     R: (nsinteger) Number {self = [super init];         if (self! = nil) {self.name = name;         Self.age = age;         Self.score = score;     Self.number = number; } return self;} Convenience builder + (ID) studentwithname: (NSString *) name Age: (Nsinteger) Age Score: (CGFloat) SCO                                      Re number: (Nsinteger) Number {Student *student = [[Student alloc] Initwithname:name       age:age Score:score Number:number]; return student;} Rewrite description-(NSString *) Description {return [NSString stringWithFormat: @ "Name:%@,age:%ld,socre :%.1f,number:%ld ", Self.name, Self.age, Self.score, Self.number];} Two students by age comparison Method-(Nscomparisonresult) Comparebyage: (Student *) Stu {   return [@ (self.age) compare:@ (stu.age )];//or the following method    return self.age > Stu.age? Nsordereddescending  : self.age = = Stu.age? nsorderedsame:nsorderedascending;} Two students by name descending method-(Nscomparisonresult) Comparebyname: (Student *) Stu {    return-[Self.name compare: Stu.name];} Two students in descending order of grades-(Nscomparisonresult) Comparebyscore: (Student *) Stu {return-[@ (Self.score) Compare: (Stu.score)];& nbsp;  //return Self.score < Stu.score? Nsordereddescending:  self.score = = Stu.score? nsorderedsame:nsorderedascending;     } //Two students follow the method of ascending the number of learners-(Nscomparisonresult) Comparebynumber: (Student *) stu {return [@ (Self.number) Compare: (Stu.number)];   //return self.num ber > Stu.number? NSOrderedDescending:self.number = = Stu.number? nsorderedsame:nsorderedascending;}

Main function (Main.h)

Student *student1 = [Student studentwithname:@ "a" age:23 score:21 number:3434343]; Student *student2 = [Student studentwithname:@ "B" age:45 score:432.4 number:324]; Student *student3 = [Student studentwithname:@ "C" age:32 score:4321.4 number:2343]; Student *student4 = [Student studentwithname:@ "D" Age:7 score:43.4 number:233];        Student *student5 = [Student studentwithname:@ "E" age:73 score:65 number:2332424]; Nsmutablearray *arr = [Nsmutablearray arraywithobjects:student1,student2,student3,student4,stud                Ent5,nil];  Sort by age Ascending [arr sortusingselector: @selector (comparebyage:)];  NSLog (@ "%@", arr);  Sort by grade descending [arr sortusingselector: @selector (comparebyscore:)];  NSLog (@ "%@", arr);  Sort by name descending [arr sortusingselector: @selector (comparebyname:)];  NSLog (@ "%@", arr);  Sort by number Ascending [arr sortusingselector: @selector (comparebynumber:)]; NSLog (@ "%@", arr);

Method 2. Sorting with block blocks syntax

       Sort by age in ascending order        [arr sortusingcomparator:^ (ID obj1,id obj2) {          return [@ (((Student *) obj1). Ages) Compare: @ (((Student * ) (OBJ2). Age)];        }];        NSLog (@ "%@", arr);                Sort by score Descending        [arr sortusingcomparator:^ (ID obj1,id obj2) {      return [@ (((Student *) obj1). Score) Compare: @ (((stude NT *) obj2). Score)];        }];                NSLog (@ "%@", arr);        Sort by name descending        [arr sortusingcomparator:^ (ID obj1,id obj2) {           return-[[(Student *) obj2 name] Compare: [(Student *) o Bj1 name] [];        }];        NSLog (@ "%@", arr);                Sort by number ascending        Nscomparator Sortblock = ^ (id obj1,id obj2) {           return [@ (((Student *) obj1). No.) Compare: @ ((( Student *) obj2)];        };        [Arr Sortusingcomparator:sortblock];        NSLog (@ "%@", arr);

"Learning the path of iOS: Objective-c" The system ordering method commonly used in OC