需要帮助在 Swift 3 中过滤核心数据

Question

我似乎找不到任何与在 Swift 3 中过滤核心数据有关的好的文档或教程。

我有以下代码：

let tempVar: String = "abcdef"

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

do {

    /* Need code to modify the fetchRequest, so that it only pulls results where the "projectID" field is equal to whatever is stored in the tempVar variable. */

    cstProjectDetails = try context.fetch(CSTProjectDetails.fetchRequest())
} catch {
    print("There was an error fetching CST Project Details.")
}

基本上，我只是想在 fetchRequest 中添加一个简单的过滤器，以便它只从“cstProjectDetails”中提取结果，其中“projectID”字段等于先前设置的变量的内容（在这种情况下， "tempVar")。

有什么想法吗？

编辑：选中的答案对我有用，但我必须快速调整请求初始化程序的代码。这是我最终得到的代码：

do {
    let request: NSFetchRequest<CSTProjectDetails> = CSTProjectDetails.fetchRequest()
    request.predicate = NSPredicate(format: "projectID == %@", cstProjectID)
    cstProjectDetails = try context.fetch(request)
    print(cstProjectDetails)
} catch {
    print("There was an error fetching CST Project Details.")
}

Answer 1

您需要在请求中附加一个谓词：

let request = CSTProjectDetails.fetchRequest()
request.predicate = NSPredicate(format: "projectID == %@", tempVar)
cstProjectDetails = try context.fetch(request)