英文:
Realm Swfit Async Write Method
问题
我刚开始接触Swift的并发编程,尤其是Realm Swift。我有两个示例代码,我认为它们是相同的,但它们不起作用。
下面是不起作用的示例代码:
var localRealm: Realm {
get {
return try! Realm()
}
}
fileprivate func testAsyncRealm() {
self.localRealm.beginAsyncWrite {
self.localRealm.create(SwiftStringObject.self, value: ["string2"])
self.localRealm.commitAsyncWrite(allowGrouping: true) { error in
print(error)
}
}
}
这段代码会引发异常:Terminating app due to uncaught exception 'RLMException', reason: Can only add, remove, or create objects in a Realm in a write transaction - call beginWriteTransaction on an RLMRealm instance first.
然而,下面的代码将可以正常工作,没有任何问题:
fileprivate func testAsyncRealm() {
let realm = try! Realm()
realm.beginAsyncWrite {
realm.create(SwiftStringObject.self, value: ["string2"])
realm.commitAsyncWrite(allowGrouping: true) { error in
print(error)
}
}
}
我在这里漏掉了什么?谢谢...
Realm 版本:10.40.0
英文:
I am new with swift concurrency especially Realm Swift. I have 2 sample codes where i think are the same, but it won't work
Below is the example of not working code
var localRealm: Realm {
get {
return try! Realm()
}
}
fileprivate func testAsyncRealm() {
self.localRealm.beginAsyncWrite {
self.localRealm.create(SwiftStringObject.self, value: ["string2"])
self.localRealm.commitAsyncWrite(allowGrouping: true) { error in
print(error)
}
}
}
This code will throw exception
Terminating app due to uncaught exception 'RLMException', reason: Can only add, remove, or create objects in a Realm in a write transaction - call beginWriteTransaction on an RLMRealm instance first.
However, below code will work without any problem
fileprivate func testAsyncRealm() {
let realm = try! Realm()
realm.beginAsyncWrite {
realm.create(SwiftStringObject.self, value: ["string2"])
realm.commitAsyncWrite(allowGrouping: true) { error in
print(error)
}
}
}
What am I missing here? Thanks...
Realm Version: 10.40.0
答案1
得分: 1
这只是一个理论,但适用于这个问题。
当一个 Realm 对象开始一个异步写事务时,似乎会在该 Realm 上设置一个标志 isPerformingAsynchronousWriteOperations
,以指示它正在进行异步写操作。例如:
var realm = try! Realm()
realm.beginAsyncWrite {
let isWrite = realm.isPerformingAsynchronousWriteOperations
print("is write? \(isWrite)") //输出 true
}
然而,在你的代码中(缩写版本):
var localRealm: Realm {
get {
return try! Realm()
}
}
fileprivate func testAsyncRealm() {
self.localRealm.beginAsyncWrite {
let isWrite = self.localRealm.isPerformingAsynchronousWriteOperations
print("is write? \(isWrite)") //输出 false
}
}
输出是 false,表示该标志未设置,因此 Realm 不认为它处于异步写状态。
我将提出这种行为是因为每次通过 self.localRealm
访问该变量时,都会重新初始化 Realm,该标志为 false。
简单的解决方案是在不重新初始化的情况下使用相同的 Realm 实例:
fileprivate func doAsyncWrite() {
var realm = self.localRealm //获取一个 Realm 实例
realm.beginAsyncWrite { //使用相同的 Realm 进行写入,这会设置标志
let isWrite = realm.isPerformingAsynchronousWriteOperations
print("is write? \(isWrite)") //返回 true
}
}
通过这种更改,问题中的代码将正确工作。
英文:
This is just a theory but fits the issue
When a realm object begins an async write transaction, it appears a flag is set on that realm isPerformingAsynchronousWriteOperations
to indicate it's in an async write. For example
var realm = try! Realm()
realm.beginAsyncWrite {
let isWrite = realm.isPerformingAsynchronousWriteOperations
print("is write? \(isWrite)") //outputs true
}
However, in your code (abbreviated)
var localRealm: Realm {
get {
return try! Realm()
}
}
fileprivate func testAsyncRealm() {
self.localRealm.beginAsyncWrite {
let isWrite = self.localRealm.isPerformingAsynchronousWriteOperations
print("is write? \(isWrite)") //outputs false
}
}
the output is false - indicating that the flag was not set so Realm doesn't think its in an asynch write.
I'll propose the behavior is because each time the var is accessed via self.localRealm
, it re-initializes Realm, with that flag being false.
The simple solution is to work with the same instance of Realm without re-initializing it
fileprivate func doAsyncWrite() {
var realm = self.localRealm //gets a realm instance
realm.beginAsyncWrite { //use that same realm to write, which sets the flag
let isWrite = realm.isPerformingAsynchronousWriteOperations
print("is write? \(isWrite)") //returns true
}
}
With that change, the code in the question works correctly.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库,让每个人都能够通过互相帮助和分享经验来进步。
评论