带有Swift的JDS字符串到NSDictionary [英] JSON String to NSDictionary with Swift
问题描述
我正在尝试从服务器中保存的数据创建字典,我收到数据但我无法将数据转换为 NSDictionary
,我相信它是保存在 NSData
对象
I am trying to create a dictionary from data that is held in a server, I receive the data but I cannot convert the data to an NSDictionary
, I believe it is held in an NSData
Object
let JSONDictionary: Dictionary = NSJSONSerialization.JSONObjectWithData(JSONData!, options: nil, error: &error) as NSDictionary
这行代码是给我这个问题的那个,它会抛出一个 BAD_EXEC_INSTRUCTION
。
This line of code is the one giving me the problem, it throws a BAD_EXEC_INSTRUCTION
.
我的问题:如何变成 JSON
进入 NSDictionary
?
MY Question: How can I turn a JSON
into an NSDictionary
?
推荐答案
您的代码不进行任何错误处理。但它可以(并且如果这些数据来自Web服务,将会以多种方式失败)。
Your code does not do any error handling. But it can (and if this data comes from a web service, will) fail in multiple ways.
- 你必须确保你的数据对象确实存在
- 你必须确保数据对象可以转换为JSON
- 你必须确保JSON实际上包含一个词典
你应该使用Swifts条件转换和它的可选绑定功能。
可选绑定如果让JSONData = JSONData
检查JSONData是不是nil 。如果无法接收数据,您使用的强制解包( JSONData!
)可能会崩溃。
You should use Swifts conditional cast and it's optional binding capabilities.
The optional binding if let JSONData = JSONData
checks that JSONData is not nil. The force unwrap (JSONData!
) you use might crash if no data could be received.
可选绑定如果让json = NSJSONSerialization.JSONObjectWithData
检查数据是否可以转换为JSON对象。条件转换为? NSDictionary
检查JSON对象是否实际上是字典。您目前不使用这些检查,将对象强制转换为NSDictionary。如果对象无效json,或者它不是字典,那么会崩溃。
The optional binding if let json = NSJSONSerialization.JSONObjectWithData
checks if the data could be converted to a JSON object. The conditional cast as? NSDictionary
checks if the JSON object is actually a dictionary. You currently don't use these checks, you cast the objects as NSDictionary. Which will crash, if the object is not valid json, or if its not a dictionary.
我建议这样的事情:
var error: NSError?
if let JSONData = JSONData { // Check 1
if let json: AnyObject = NSJSONSerialization.JSONObjectWithData(JSONData, options: nil, error: &error) { // Check 2
if let jsonDictionary = json as? NSDictionary { // Check 3
println("Dictionary received")
}
else {
if let jsonString = NSString(data: JSONData, encoding: NSUTF8StringEncoding) {
println("JSON String: \n\n \(jsonString)")
}
fatalError("JSON does not contain a dictionary \(json)")
}
}
else {
fatalError("Can't parse JSON \(error)")
}
}
else {
fatalError("JSONData is nil")
}
您可以将检查2和3合并到一行并检查NSJSONSerialization是否可以直接创建NSDictionary:
You could merge check 2 and 3 into one line and check if NSJSONSerialization can create a NSDictionary directly:
var error: NSError?
if let JSONData = JSONData { // Check 1.
if let JSONDictionary = NSJSONSerialization.JSONObjectWithData(JSONData, options: nil, error: &error) as? NSDictionary { // Check 2. and 3.
println("Dictionary received")
}
else {
if let jsonString = NSString(data: JSONData, encoding: NSUTF8StringEncoding) {
println("JSON: \n\n \(jsonString)")
}
fatalError("Can't parse JSON \(error)")
}
}
else {
fatalError("JSONData is nil")
}
确保在生产代码中使用适当的错误处理替换 fatalError
Make sure to replace fatalError
with appropriate error handling in your production code
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