核心数据迁移问题：storePath无法启动

Question

我尝试将一些核心数据代码从swift2迁移到swift4。代码如下：

///  Removes the existing model store specfied by the receiver.
///
///  - returns: A tuple value containing a boolean to indicate success and an error object if an error occurred.
public func removeExistingModelStore() -> (success: Bool, error: NSError?) {
    var error: NSError?
    let fileManager = FileManager.default

    if let storePath = storeURL.path {
        if fileManager.fileExists(atPath: storePath) {
            let success: Bool
            do {
                try fileManager.removeItem(at: storeURL)
                success = true
            } catch let error1 as NSError {
                error = error1
                success = false
            }
            if !success {
                print("*** \(String(describing: CoreDataModel.self)) ERROR: [\(#line)] \(#function) Could not remove model store at url: \(String(describing: error))")
            }
            return (success, error)
        }
    }

    return (false, nil)
}

构建错误显示 "Initializer for conditional binding must have Optional type, not 'String'"。所以我用谷歌搜索并遵循了删除可选绑定的建议：

let storePath = storeURL.path { ... }

然后在上面的地方又出现了两个新的错误：1. 不能调用非函数类型的值'String'； 2.变量在其自身初始值范围内使用

我相信上面的代码主要是 setup/teardown 核心数据模型的样板代码。我是初学者所以请帮助！

Answer 1

如果你从if let中删除了if，那么你也必须删除{ }，你可以试试

public func removeExistingModelStore() -> (success: Bool, error: Error?) {

    if FileManager.default.fileExists(atPath: storeURL.path ) {

        do {
            try FileManager.default.removeItem(at: storeURL)
             return (true, nil) 
        } catch {

            return (false, error)  
        }

     } 

    return (false, nil)
}

核心数据迁移问题：storePath无法启动

core data migration issue: storePath cannot be initiated

core-data

ios

swift

swift2