OC中关于字典(可变字典)的使用---连载三
可变字典使用举例：
设计一个学生类Student, 有这些属性：name(姓名)、age(年龄)、score(分数)、(classNum)班级
（1）将如下学生添加到数组中
姓名 年龄 分数 班级
Tom 17 82 Class01
Jim 22 75 Class01
Jerry 34 54 Class01
Owen 22 98 Class04
Steve 19 77 Class05
（2）计算所有学生的平均分（年级的平均分）
（3）计算各个班级的平均分
（4）用名字作为key, value是学生对象，将这些学生存入字典。
main.m-------------------------------------------------------
int main(int argc, const char * argv[]) {
@autoreleasepool {
/* 第1步：添加学生到数组中 */
// 创建学生类-构建对象
// Tom
Student *tom = [[Student alloc] initWithName:@"Tom"
WithAge:17
WithScore:82
WithClassBan:@"Class01"];
// Jim
Student *jim = [[Student alloc] initWithName:@"Jim"
WithAge:22
WithScore:75
WithClassBan:@"Class01"];
// Jerry
Student *jerry = [[Student alloc] initWithName:@"Jerry"
WithAge:34
WithScore:54
WithClassBan:@"Class01"];
// Owen
Student *owen = [[Student alloc] initWithName:@"Owen"
WithAge:22
WithScore:98
WithClassBan:@"Class04"];
// Steve
Student *steve = [[Student alloc] initWithName:@"Steve"
WithAge:19
WithScore:77
WithClassBan:@"Class05"];
// 将学生添加入数组
NSMutableArray *arrayStudent = [NSMutableArray arrayWithObjects:tom, jim, jerry, owen, steve, nil];
//计算所有学生的平均分（年级的平均分）
CGFloat sum = 0;
for (Student *stu in arrayStudent) {
sum += stu.score;
}
NSLog(@"平均分：%.2f", sum / arrayStudent.count);
//计算各个班级的平均分
//字典
/*
{
@"class1": [tom, jerry]}
@"class2": [keven, jobs]}
}
*/
NSMutableDictionary *mDic = [NSMutableDictionary dictionary];
for (Student *stu in arrayStudent) {
//从学生中获取学生所在的班级
NSString *classNum = stu.classNum;
NSMutableArray *mArr = [mDic objectForKey:classNum];
//判断可变数组是否存在,如果不存在，则初始化此数组
if (mArr == nil) {
mArr = [NSMutableArray array];
[mDic setObject:mArr forKey:classNum];
}
//把学生添加到可变数组中
[mArr addObject:stu];
}
NSLog(@"mDic is %@", mDic);
//通过遍历字典 算出每个班的平均分
for (NSString *key in mDic) {
NSMutableArray *mArr = mDic[key];
CGFloat sum = 0;
for (Student *stu in mArr) {
sum += stu.score;
}
NSLog(@"%@班级的平均分为%.2f", key, sum / mArr.count);
}
// 用名字作为key, value是学生对象，将这些学生存入字典。
NSMutableDictionary *stuDic = [NSMutableDictionary dictionary];
for (Student *stu in arrayStudent) {
NSString *key = stu.name;
[stuDic setObject:stu forKey:key];
}
NSLog(@"stuDic is %@", stuDic);
}
return 0;
}
Student.h(学生类)-----------------------------------------------------------------------
@interface Student : NSObject
// 定义学生属性
{ // 姓名
NSString *_name;
// 年龄
NSInteger _age;
// 分数
NSInteger _score;
// 班级
NSString *_classNum;
}
// 定义方法
#pragma mark -(自定义初始化方法)
- (id)initWithName:(NSString *)name
WithAge:(NSInteger)age
WithScore:(NSInteger)score
WithClassBan:(NSString *)classNum;
#pragma mark -Set
#pragma mark -Get
- (NSString *)name;
- (NSInteger)age;
- (NSInteger)score;
- (NSString *)classNum;
@end
Student.m------------------------------------------------------------------------------
#import "Student.h"
@implementation Student
#pragma mark -(自定义初始化方法)
- (id)initWithName:(NSString *)name
WithAge:(NSInteger)age
WithScore:(NSInteger)score
WithClassBan:(NSString *)classNum
{
self = [super init];
if (self) {
//..
_name = name;
_age = age;
_score = score;
_classNum = classNum;
}
return self;
}
#pragma mark -Set
#pragma mark -Get
- (NSString *)name
{
return _name;
}
- (NSInteger)age
{
return _age;
}
- (NSInteger)score
{
return _score;
}
- (NSString *)classNum
{
return _classNum;
}
@end