Question

我正在尝试基于段控制器开关定义谓词。

if self.streamtype == "case1" {
    let predicatearray = defaults.object(forKey: "case1") as! [String]
    let predicate = NSPredicate(format: "UserID IN %@" , predicatearray)
} else if self.streamtype == "case2" {
    let predicate = NSPredicate(format: "TRUEPREDICATE", argumentArray: nil)
} else {
    let predicatearray = defaults.object(forKey: "case3") as! [String]
    let predicate = NSPredicate(format: "UserID IN %@", predicatearray)
}

let publicData = CKContainer.default().publicCloudDatabase
let query = CKQuery(recordType: "Post", predicate: predicate)

我收到错误说：

＆＃34;无法发送到NSPredicate类的抽象对象：创建一个具体的实例！＆＃34;

另外，它告诉我从未使用过谓词变量的初始化。我尝试用几种不同的方式编写函数，但这对我来说最有意义，因为我只需要在加载新信息时更新谓词，所以我只将两个函数放在一起。

Answer 1

您在if {}或else {}范围内定义谓词，这就是为什么它在范围之外不可见。

var predicate : NSPredicate!
if self.streamtype == "case1" {
    let predicatearray = defaults.object(forKey: "case1") as! [String]
    predicate = NSPredicate(format: "UserID IN %@", predicatearray)
} else if self.streamtype == "case2" {
    predicate = NSPredicate(format: "TRUEPREDICATE", argumentArray: nil)
} else {
    let predicatearray = defaults.object(forKey: "case3") as! [String]
    predicate = NSPredicate(format: "UserID IN %@", predicatearray)
}

let publicData = CKContainer.default().publicCloudDatabase
let query = CKQuery(recordType: "Post", predicate: predicate)

if else语句定义NSPredicate

1 个答案: