zoukankan      html  css  js  c++  java
  • Core Data 多表连接及查询

    一:先建议两张表

    1. Person,Score 分别代表,学生表,分数表
    2. 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);
        }
        
        
    }
  • 相关阅读:
    关于任意文件下载及上传漏洞
    一文掌握XSS
    WEB层知识点
    课程交流网站项目架构
    docker容器中启动uwsgi秒退
    mongoDB中update_one与find_one_update异同
    Vue集成CKEditor5源代码
    Vue的index.html与其他静态文件分离部署
    scrapy-redis分布式爬虫使用及docker swarm集群部署
    django中form组件的校验时raise ValidationError与self.add_error异同
  • 原文地址:https://www.cnblogs.com/cocoajin/p/3492587.html
Copyright © 2011-2022 走看看