在字典上对成员“下标"的引用含糊不清

问题描述

我正在尝试为一个类创建一个失败的初始化器.我的课程将使用网络请求中的输入进行初始化.网络不可靠，我想创建一个初始化程序来检查所有属性的存在，否则将失败.

I am trying to create a failable initializer for a class. My class will be initialized using input from a network request. Networks being unreliable, I want to create an initializer the checks for the presence on all properties, and for it to fail otherwise.

我在这里尝试使用警惕，所以请随时指出该方法中的任何明显错误:

I am trying to make use of guard here, so please feel free to point any obvious mistakes in the approach:

public class JobModel {
    let jobId: String
    let status: String
    let toName: String
    let toAddress: String
    let description: String
    let fee: Int
    let jobDate: NSDate
    let fromName: String
    let fromAddress: String

    init?(job: [String:AnyObject]) throws {
        guard self.jobId = job["jobid"] as! String else {
            throw InitializationError.MissingJobId
        }

    }
}

guard self.jobId行无法编译，出现错误:Ambiguous reference to member 'subscript'

The guard self.jobId line is failing to compile, with error:Ambiguous reference to member 'subscript'

关于如何纠正此错误的任何想法?

Any ideas on how to correct this error?

推荐答案

guard需要符合BooleanType的条件.简单分配不是.您将需要这样的东西.

guard requires a condition that conforms to BooleanType. Simple assignment doesn't. You would need something like this.

guard let j = job["jobid"] as? String else {
    throw InitializationError.MissingJobId
}
self.jobId = j

但是，您将收到错误消息:从实例化器抛出类之前，必须先初始化类实例的所有存储属性".这是预期的，并在The Swift Programming Language中进行了记录:

However, then you'll get the error "all stored properties of a class instance must be initialized before throwing from an initializer." This is expected and documented in the The Swift Programming Language:

克里斯·拉特纳(Chris Lattner)在此处提到当前行为是不受欢迎的: http ://swift-language.2336117.n4.nabble.com/Swift-2-throwing-in-initializers-td439.html

Chris Lattner mentions the current behavior is undesirable here: http://swift-language.2336117.n4.nabble.com/Swift-2-throwing-in-initializers-td439.html

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