Realm是用来代替CoreData和SQLite的数据存储方式，支持的类型有Bool,Int16,Int32,Int64,Double,Float,String,Date,Data

在swift中，创建一个Dog类，继承自Object，如下所示：

 class Dog: Object {
 @objc dynamic var name = ""
 @objc dynamic var age = 0
 @objc dynamic var key = 0
 //主键
 override static func primaryKey() -> String? {
 return "key"
 }
 }

然后在创建一个Person类，同样继承自Object类，在Person类中可能拥有多个dog属性，如下：

 class Person: Object {
 @objc dynamic var name = ""
 @objc dynamic var age = 0
 @objc dynamic var isEat = false
 var dogs = List<Dog>()
 }

在Realm中List相当于swift中的数组，要声明List中的数据类型。

增，删，改，查

• 添加一个dog对象

    let realm = try! Realm()
    let myDog = Dog()
    
    myDog.name = "canader"
    myDog.key = 1
    myDog.age = 20
    
    //增
    try! realm.write {
    realm.add(myDog)
    }
    
    //删
    try! realm.write {
    
        //删除myDog
    realm.delete(myDog)
    //删除所有
    realm.deleteAll()
    }
  
    //改
    try! realm.write {
    myDog.name = "JACK"
    }
    
    //通过主键更新
     try! realm.write {
        //如果有主键为默认值的对象，那么久更新
    realm.add(myDog, update: true)
    }
    
    //通过键值编码更新属性
    try! realm.write {
    myDog.setValue("Rose", forKeyPath: "name")
    }
    
    //查
    //获取所有的dog属性
    let result = realm.objects(Dog.self)
    
    //过滤获取到的Dog属性
    let result = realm.objects(Dog.self).filter("age > 0")
  

• 添加一个person对象

    //增
    let dog2 = Dog()
    dog2.name = "dog2"
    dog2.age = 10
    dog2.key = 2
  
    let person1 = Person()
    person1.name = "wangwu"
    person1.age = 20
    person1.isEat = true
    //给Person的dogs属性添加对象
    person1.dogs.append(myDog)
    person1.dogs.append(dog2)
    try! realm.write {
    realm.add(person1)
    }
    
    
    //删
    try! realm.write {
    realm.delete(persons)
    }
    
    
    //改
    let result = realm.objects(Person.self)
    print(result.count)
    for i in 0..<result.count {
    let p = result[i]
    print(p.name, p.dogs.count)
    }
    
    //查
    let persons = realm.objects(Person.self).filter("age == 20")
    for i in 0..<persons.count {
    let p = persons[i]
    try! realm.write {
      p.name = "modifity"
    }
    print(p.name)
    }