我想用“id”键对数据进行排序,我如何理解NSPredicate
格式的格式字符串是什么?我有一个 100 号码的帖子。
我的代码:
let objectIDs = posts.map{$0.id}
let predicate = NSPredicate(format: "self IN %@", objectIDs)
let sortByUserId = NSSortDescriptor(key: "id", ascending: true)
我的描述有误:
can not parse "self IN %@" format string.
解析 JSON 数据的代码:
func postsFromJSONData(data : NSData, inContext context: NSManagedObjectContext) -> PostResult {
do{
let jsonObject : [[String:AnyObject]]
= try NSJSONSerialization.JSONObjectWithData(data, options: []) as! [[String:AnyObject]]
for postJSON in jsonObject {
if let post = postFromJsonObject(postJSON, incontext : context) {
finalPost.append(post)
}
}
return .Sucsess(finalPost)
}
catch let error {
return .Failure(error)
}
}
当网络服务完成时获取主队列帖子:
func fetchRecentPost(completion completion: (PostResult) -> Void){
let request = NSURLRequest(URL: recentPostURL(["":""]))
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) in
var result = self.processRecentPostRequest(data: data, error: error)
if case let .Sucsess(posts) = result {
let mainQueueContext = self.coreDataStack.mainQueueContext
mainQueueContext.performBlockAndWait(){
try! mainQueueContext.obtainPermanentIDsForObjects(posts)
}
let objectIDs = posts.map{$0.id}
let predicate = NSPredicate(format: "self IN %@", objectIDs)
let sortByUserId = NSSortDescriptor(key: "id", ascending: true)
do{
try self.coreDataStack.saveChanges()
let mainQueuePosts = try self.fetchMainQueuePosts(predicate: predicate, sortDiscriptors: [sortByUserId])
result = .Sucsess(mainQueuePosts)
}
catch let error {
result = .Failure(error)
}
}
completion(result)
})
最佳答案
你的预测应该是这样的
let predicate = NSPredicate(format: "id IN %@", objectIDs)
let sortByUserId = NSSortDescriptor(key: "id", ascending: true)
注意:要么是self.id IN %@
,要么是id IN %@
。
关于ios - onFormat string For NSPredicate,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44365700/