ios 在 Swift (2.0) 中正确处理 NSJSONSerialization (try catch)？

Correct handling of NSJSONSerialization (try catch) in Swift (2.0)?

提问by Mirko Brunner

arowmy init works fine in Swift < 2 but in Swift 2 I get a error message from Xcode Call can throw, but it is not marked with 'try' and the error is not handledat let anyObj = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]. I think in my case I can′t use a try catch block because super is not initialized at this time. "Try" need a function that throws.

arowmy初始化工作正常斯威夫特<2，但是在斯威夫特2我在Xcode得到一个错误信息Call can throw, but it is not marked with 'try' and the error is not handled的let anyObj = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]。我认为就我而言，我不能使用 try catch 块，因为此时 super 未初始化。“尝试”需要一个抛出的函数。

here is my function:

这是我的功能：

required init(coder aDecoder : NSCoder)
{
    self.name  = String(stringInterpolationSegment: aDecoder.decodeObjectForKey("name") as! String!)
    self.number = Int(aDecoder.decodeIntegerForKey("number"))
    self.img = String(stringInterpolationSegment: aDecoder.decodeObjectForKey("image") as! String!)
    self.fieldproperties = []

    var tmpArray = [String]()
    tmpArray = aDecoder.decodeObjectForKey("properties") as! [String]


    let c : Int = tmpArray.count
    for var i = 0; i < c; i++
    {
        let data : NSData = tmpArray[i].dataUsingEncoding(NSUTF8StringEncoding)!

         // Xcode(7) give me error: 'CAll can thorw, but it is not marked with 'try' and the error is not handled'
        let anyObj =  NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]

        let label = anyObj["label"] as AnyObject! as! String
        let value = anyObj["value"] as AnyObject! as! Int
        let uprate = anyObj["uprate"] as AnyObject! as! Int
        let sufix = anyObj["sufix"] as AnyObject! as! String

        let props = Fieldpropertie(label: label, value: value, uprate: uprate, sufix: sufix)
        self.fieldproperties.append(props)
    }
}

Xcode mean that: let anyObj = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]

Xcode 的意思是： let anyObj = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]

but I have no idea to do here the right think according to this document https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html

但我不知道根据本文档https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html在这里做正确的思考

回答by Rob

The jsonObjectcan throwerrors, so put it within doblock, use try, and catchany errors thrown. In Swift 3:

该jsonObject罐throw的错误，所以把它内do块，使用try和catch出现的任何错误。在 Swift 3 中：

do {
    let anyObj = try JSONSerialization.jsonObject(with: data) as! [String: Any]

    let label = anyObj["label"] as! String
    let value = anyObj["value"] as! Int
    let uprate = anyObj["uprate"] as! Int
    let sufix = anyObj["sufix"] as! String

    let props = Fieldpropertie(label: label, value: value, uprate: uprate, sufix: sufix)

    // etc.
} catch {
    print("json error: \(error.localizedDescription)")
}

Or, in Swift 4, you can simplify your code by making your structconform to Codable:

或者，在 Swift 4 中，您可以通过使您struct符合以下条件来简化您的代码Codable：

struct Fieldpropertie: Codable {
    let label: String
    let value: Int
    let uprate: Int
    let suffix: String
}

Then

然后

do {
    let props = try JSONDecoder().decode(Fieldpropertie.self, from: data)
    // use props here; no manual parsing the properties is needed
} catch {
    print("json error: \(error.localizedDescription)")
}

For Swift 2, see previous revision of this answer.

对于 Swift 2，请参阅此答案的先前修订版。

回答by Gerd Castan

JSONSerialization.JSONObject throws ErrorType and not NSError.

JSONSerialization.JSONObject 抛出 ErrorType 而不是 NSError。

so the correct catch is

所以正确的捕获是

do {
    let anyObj = try JSONSerialization.JSONObject(with: data, options: []) as! [String:AnyObject]
    // use anyObj here
} catch let error {
    print("json error: \(error)")
}

The type of errorin catch let erroris ErrorType

errorin的类型catch let error是ErrorType

回答by trevorj

Don't know if it'll solve your problem, but isn't the method JSONObjectWithData:options:error:? I think you're missing the errorparameter.

不知道它是否会解决您的问题，但不是方法JSONObjectWithData:options:error:吗？我认为您缺少error参数。