关于字典中key的排序的自己的一些见解 - 黑马程序员技术交流社区

#import "TRStudent.h"
@implementation TRStudent
-(NSUInteger)hash{
NSLog(@"hash方法执行了");
return [super hash];
//return 1;
}
-(BOOL)isEqual:(id)object{
NSLog(@"isEqual方法执行了");
return [super isEqual:object];
/*
//1.自反性
if(self == object){//两个引用指向同一个对象
return YES;
}else{
//2.类型是否相同如果类型不相同肯定不同
if(![object isMemberOfClass:[TRStudent class]]){
return NO;
}else{//两个对象的类型相同
//3.才比较对象的值
TRStudent *otherStu = object;
if (self.age==otherStu.age&&[self.name isEqualToString:otherStu.name]) {
return YES;
}else{
return NO;
}
}
}
return NO;
*/
}
-(id)initWithAge:(int)age andName:(NSString*)name{
self = [super init];
if (self) {
self.age = age;
self.name = name;
}
return self;
}
+(TRStudent*)studentWithAge:(int)age andName:(NSString*)name{
return [[TRStudent alloc]initWithAge:age andName:name];
}
-(NSComparisonResult)compare:(TRStudent*)otherStudent{
return [self.name compare:otherStudent.name];
}
@end

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#import <Foundation/Foundation.h>
#import "TRStudent.h"
int main(int argc, const char * argv[])
{
@autoreleasepool {
TRStudent *stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan"];1.新建各个学生对象
TRStudent *stu2 = [TRStudent studentWithAge:19 andName:@"lisi"];
TRStudent *stu3 = [TRStudent studentWithAge:20 andName:@"wangwu"];
TRStudent *stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu"];
NSDictionary *stus = [NSDictionary dictionaryWithObjectsAndKeys:stu1,stu1.name,stu2,stu2.name,stu3,stu3.name,stu4,stu4.name, nil];2.将新建的学生对象放入一个字典中
//排序前3.1第一种排序方法
NSArray *allKeys = [stus allKeys];
for (NSString *key in allKeys) {
//key->value
TRStudent *stu = stus[key];
NSLog(@"name:%@ age:%d",stu.name,stu.age);
}
//排序后
//1.排序的第一种方式无法对字典进行排序只能对key进行排序
/*
NSArray *sortedAllKeys = [allKeys sortedArrayUsingSelector:@selector(compare:)];
for (NSString *key in sortedAllKeys) {
//key->value
TRStudent *stu = stus[key];
NSLog(@"name:%@ age:%d",stu.name,stu.age);
}
*/
//2.字典排序方式2 3.2第二种排序方法
NSArray *sortedAllKeys = [stus keysSortedByValueUsingSelector:@selector(compare:)];
for (NSString *key in sortedAllKeys) {
//key->value
TRStudent *stu = stus[key];
NSLog(@"name:%@ age:%d",stu.name,stu.age);
}
NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:@1,@"one",@2,@"two", nil];
[dic writeToFile:@"/Users/yr/Desktop/dic.xml" atomically:NO];4.将排序好的对象写进dic.xml文件中
}
return 0;
}

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一共有两种排序方法，在TRStudent.h和TRStudent.m文件中建立一个student对象，.h文件是对该对象属性方法的申明，.m文件是对该对象具体属性和方法的实现，然后在main.m中新建该对象，对他进行赋值，从而得到对字典中的key的排序的一个范例

#import <Foundation/Foundation.h>
#import "TRStudent.h"
int main(int argc, const char * argv[])
{
@autoreleasepool {
TRStudent *stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan"];
TRStudent *stu2 = [TRStudent studentWithAge:19 andName:@"lisi"];
TRStudent *stu3 = [TRStudent studentWithAge:20 andName:@"wangwu"];
TRStudent *stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu"];
NSDictionary *stus = [NSDictionary dictionaryWithObjectsAndKeys:stu1,stu1.name,stu2,stu2.name,stu3,stu3.name,stu4,stu4.name, nil];
//排序前
NSArray *allKeys = [stus allKeys];
for (NSString *key in allKeys) {
//key->value
TRStudent *stu = stus[key];
NSLog(@"name:%@ age:%d",stu.name,stu.age);
}
//排序后
//1.排序的第一种方式无法对字典进行排序只能对key进行排序
/*
NSArray *sortedAllKeys = [allKeys sortedArrayUsingSelector:@selector(compare:)];
for (NSString *key in sortedAllKeys) {
//key->value
TRStudent *stu = stus[key];
NSLog(@"name:%@ age:%d",stu.name,stu.age);
}
*/
//2.字典排序方式2
NSArray *sortedAllKeys = [stus keysSortedByValueUsingSelector:@selector(compare:)];
for (NSString *key in sortedAllKeys) {
//key->value
TRStudent *stu = stus[key];
NSLog(@"name:%@ age:%d",stu.name,stu.age);
}
NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:@1,@"one",@2,@"two", nil];
[dic writeToFile:@"/Users/yr/Desktop/dic.xml" atomically:NO];
}
return 0;
}

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