Core Data 多表连接及查询

分类: IT文章 • 2023-03-24 14:30:30

一：先建议两张表

Person,Score 分别代表，学生表，分数表
在 Person的Relationships里面建立关系，指向分数score

二：coreData生成的两个表：

Person

@class Score;

@interface Person : NSManagedObject

@property (nonatomic, retain) NSString * address;
@property (nonatomic, retain) NSNumber * age;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) Score *score;

@end

View Code

　　Score

@interface Score : NSManagedObject

@property (nonatomic, retain) NSNumber * dotNet;
@property (nonatomic, retain) NSNumber * java;
@property (nonatomic, retain) NSNumber * php;

@end

View Code

三：添加记录查询记录代码

- (void)addTheRowData
{
    Person *person = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.appDelegate.managedObjectContext];
    person.name = @"李四";
    person.age = [NSNumber numberWithInt:20];
    person.address = @"中国济南";
    
    Score *score = [NSEntityDescription insertNewObjectForEntityForName:@"Score" inManagedObjectContext:self.appDelegate.managedObjectContext];
    score.dotNet = [NSNumber numberWithFloat:70.77];
    score.php = [NSNumber numberWithFloat:80.88];
    score.java = [NSNumber numberWithFloat:90.99];
    
    person.score = score;
    //score.person = person;
    
    
    [self.appDelegate saveContext];
    
}

- (void)showTheTableData
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]initWithEntityName:@"Person"];
    NSError *error;
    NSArray *fetchedObjects = [self.appDelegate.managedObjectContext executeFetchRequest:fetchRequest error:&error];
    for (Person *info in fetchedObjects) {
        //Score *score = info.score;
        NSLog(@"name:%@ age:%@ address:%@ --- dotNet:%@ java:%@ php:%@", info.name,info.age,info.address,info.score.dotNet,info.score.java,info.score.php);
    }
    
    
}

Core Data 多表连接及查询

相关推荐