oc实现小型学生管理系统

                       
  首先，创建一个工程，然后加入两个cocoaclass，分别命名为Student   和 StudentSystem.
   然后就可以开始写代码喽
     1.Student类--Student.h文件
```
 #import
@interface Student : NSObject
{
@protected
    int stuID;
    NSString * name;
    int age;
    int score;
}
@property int stuID;
@property NSString * name;
@property int age;
@property int score;
-(id)init;
-(void)inputStudent;
-(void)printStudent;
//-(void)modifyStudent;
@end
  
```

 2.Student类--Student.m文件
```
#import "Student.h"
int allgrades=0;
@implementation Student
//extern int allgrades;
@synthesize stuID,name,age,score;
-(id)init//构造函数
{
    if (self = [super init]) {
        stuID = 0;
        name = nil;
        age = 0;
        score = 0;
    }
    else
    {
        self = nil;
    }
    return self;
}
-(void)inputStudent
{
    NSLog(@"请依次输入学生的姓名,学号,年龄,成绩(格式:ganyu 10086 18 100)");
    char CharName[20];
    int intId;
    int intAge,intScore;
    scanf("%s %d %d %d",CharName,&intId,&intAge,&intScore);
    allgrades+=intScore;
    [self setName:[[NSString alloc]initWithUTF8String:CharName]];
    [self setStuID:intId];
    [self setAge:intAge];
    [self setScore:intScore];
}
-(void)printStudent
{
    NSLog(@"学号:%d,姓名:%@,年龄:%d,成绩: %d",self.stuID,self.name,self.age,self.score);
}
-(void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeInt:stuID forKey:@"id"];
    [aCoder encodeObject:name forKey:@"name"];
    [aCoder encodeInt:age forKey:@"age"];
    [aCoder encodeInt:score forKey:@"score"];
}
-(id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super init]) {
        self.stuID = [aDecoder decodeIntForKey:@"id"];
        self.name = [aDecoder decodeObjectForKey:@"name"];
        self.age = [aDecoder decodeIntForKey:@"age"];
        self.score = [aDecoder decodeIntForKey:@"score"];
    }
    return self;
}
@end

```
3.StudentSystem类--StudentSystem.h 文件

```
#import
#import "Student.h"
extern int allgrades;
@interface StudentSystem : NSObject
@property NSMutableArray *studentArray;
-(id)init;
-(void)printStudentArray;
-(void)addStudentArray:(Student *)stu;
-(void)findStudentByStuID;
-(void)removeStudentArrayByStuID;
-(void)writeToFile;
-(void)readFromFile;
-(void)countStudent;
-(void)SortStudentArray;// >0升序,<0降序
-(void)motifyStudent;
@end

```

4.StudentSystem类--StudentSystem.m文件

```
#import "StudentSystem.h"
extern int allgrades;
@implementation StudentSystem
@synthesize studentArray;
-(id)init
{
    if (self = [super init]) {
        studentArray = [[NSMutableArray alloc]init];
    }
    else
        self = nil;
    return self;
}
-(void)countStudent
{
    unsigned long int a=[self.studentArray count];
    NSLog(@"一共有%lu 位同学",a);
    double b=allgrades/a;
    NSLog(@"allgrades的值为:%d",allgrades);
    NSLog(@"大家的平均成绩是%lf",b);
}
-(void)printStudentArray
{
    for (Student *stu in studentArray) {
        [stu printStudent];
    }
    NSLog(@"array 打印完毕.");
}
-(void)addStudentArray:(Student *)stu
{
    [[self studentArray] addObject:stu];
    NSLog(@"添加完成");
}
-(void)findStudentByStuID
{
    NSLog(@"请输入你要查找的同学的学号:");
    int studentID;
    scanf("%d",&studentID);
    for (Student *stu in studentArray) {
        if (stu.stuID == studentID) {
            [stu printStudent];
            return ;
        }
    }
    NSLog(@"未找到学号为%d的学生.",studentID);
}
-(void)removeStudentArrayByStuID
{
    NSLog(@"请输入你要删除的同学的学号:");
    int studentID;
    scanf("%d",&studentID);
    for (Student *stu in studentArray) {
        if (stu.stuID == studentID) {
            [studentArray removeObject:stu];
            allgrades-=stu.score;
            NSLog(@"删除完成.");
            return ;
        }
    }
    NSLog(@"未找到学号为%d的学生.",studentID);
}
-(void)SortStudentArray// >0升序,<0降序
{
    NSLog(@"按照学号排序请输入 (id)");
    NSLog(@"按姓名排序请输入(name)");
    NSLog(@"按照年龄排序请输入(age)");
    NSLog(@"按照成绩排序请输入(score)");
    char charKey[10] ;
    scanf("%s",charKey);
    NSString *tempkey = [NSString stringWithUTF8String:charKey];
    NSString *key = [tempkey lowercaseString];
    BOOL ascending = NO;
if ([key isEqualToString:@"id"]) {
        NSSortDescriptor *sortByID = [NSSortDescriptor sortDescriptorWithKey:@"stuID" ascending:ascending];
        [studentArray sortUsingDescriptors:[NSArray arrayWithObject:sortByID]];
    }
    else if([key isEqualToString:@"name"])
    {
        NSSortDescriptor *sortByName= [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:ascending];
        [studentArray sortUsingDescriptors:[NSArray arrayWithObject:sortByName]];
    }
    else if([ key isEqualToString:@"age"])
    {
        NSSortDescriptor *sortByAge = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:ascending];
        [studentArray sortUsingDescriptors:[NSArray arrayWithObject:sortByAge]];
    }
    else if ([key isEqualToString:@"score"])
    {
        NSSortDescriptor *sortByScore = [NSSortDescriptor sortDescriptorWithKey:@"score" ascending:ascending];
        [studentArray sortUsingDescriptors:[NSArray arrayWithObject:sortByScore]];
    }
}
-(void)writeToFile
{
    NSString *path = [NSString stringWithFormat:@"/Users/len/Desktop"];
    NSLog(@"请输入你所要写入的文件名字:");
    char sfilename[20];
    scanf("%s",sfilename);
    NSString *filename = [NSString stringWithUTF8String:sfilename];
    NSString *filepath = [path stringByAppendingPathComponent:filename];
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:studentArray ];
    [data writeToFile:filepath atomically:YES];
}
-(void)readFromFile
{
    NSString *path = [NSString stringWithFormat:@"/Users/len/Desktop"];
    NSLog(@"请输入你所要读取的文件名字:");
    char sfilename[20];
    scanf("%s",sfilename);
    NSString *filename = [NSString stringWithUTF8String:sfilename];
    NSString *filepath = [path stringByAppendingPathComponent:filename];
    //NSMutableData *data = [[NSMutableData alloc]initWithContentsOfFile:filepath];
    NSMutableData *Data = [NSMutableData dataWithContentsOfFile:filepath];
    self.studentArray = [NSKeyedUnarchiver unarchiveObjectWithData:Data];
}
-(void)motifyStudent
{
    NSLog(@"请输入你要修改的同学的学号:");
    int studentID;
    scanf("%d",&studentID);
    for (Student *stu in studentArray) {
        if (stu.stuID == studentID) {
            NSLog(@"修改学号为%d的姓名,年龄,成绩(格式:ganyu 10086 18 100)",studentID);
            allgrades-=[stu score];
            char CharName[20];
            int intId;
            int intAge,intScore;
            scanf("%s %d %d %d",CharName,&intId,&intAge,&intScore);
            [stu setName:[[NSString alloc]initWithUTF8String:CharName]];
            [stu setStuID:intId];
            [stu setAge:intAge];
            [stu setScore:intScore];
            allgrades+=[stu score];
            return ;
        }
    }
    NSLog(@"未找到学号为%d的学生.",studentID);
}
@end

```
5.main文件

```
#import
#import "Student.h"
#import "StudentSystem.h"
int main(int argc, const char * argv[])
{
    @autoreleasepool {
        NSLog(@"欢迎来到计科某班考试成绩管理系统");
        StudentSystem *class= [[StudentSystem alloc]init];
        while (YES) {
            NSLog(@"1:增加 2:打印");
            NSLog(@"3:删除 4:查找");
            NSLog(@"5:写入 6:读出");
            NSLog(@"7:统计 8:排序");
            NSLog(@"9:修改 0:退出");
            int c;
            scanf("%d",&c);
            switch (c) {
                case 1:
                {
                    Student *stuTemp = [[Student alloc]init];
                    [stuTemp inputStudent];
                    [class addStudentArray:stuTemp];
                    break;
                }
                case 2:
                    [class printStudentArray];
                    break;
                case 3:
                    [class removeStudentArrayByStuID];
                    break;
                case 4:
                    [class findStudentByStuID];
                    break;
                case 5:
                    [class writeToFile];
                    break;
                case 6:
                    [class readFromFile];
                    break;
                case 7:
                    [class countStudent];
                    break;
                case 8:
                    [class SortStudentArray];
                    NSLog(@"已排序");
                    break;
                case 9:
                    [class motifyStudent];
                    break;
                case 0:
                    return 0;
                default:
                    break;
            }
        }
    }
    return 0;
}

```
//关于上面还有一些功能没有实现，有兴趣的话可以尝试一下呦