ios - 从文件中读取 JSON 数据 Swift 2.0 适用于模拟器但不适用于设备，返回 json null

Question

您好，我正在尝试从我的应用程序中的文件写入和读取一些数据 JSON 格式。我知道设备上的文件名是按键敏感的，我检查了两次。我的问题是理解为什么它在模拟器上运行良好并在设备上返回 null JSON 数据。非常感谢!

func writeJsonData() {

    let file = "/settings.json"
    if let dir :  NSString = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true).first {
        let path = dir.stringByAppendingPathComponent(file);
            let json =  ["val1":1, "val2":2]
            self.jsonToNSData(json)
            if let file = NSFileHandle(forWritingAtPath:path) {
                file.writeData(jsonToNSData(json)!)
        }
    }

    self.readJsonData()
}

func readJsonData () {

    let file = "/settings.json"
    if let dir :  NSString = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true).first {
        let path = dir.stringByAppendingPathComponent(file);
        if let data = NSData(contentsOfFile: path as String) {
            let json = JSON(data: data)
            print(json)  // !!!!!!!!!!!
            if json != JSON.null {

                let val1 = json["val1"].int!
                let val2 = json["val2"].int!
            }
        }
    }
}

问题出在写入数据上，正确的方法是:

func writeJsonData() {
        let file = "file.json"
        if let dir :  NSString = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true).first {
            let path = dir.stringByAppendingPathComponent(file);
                let json: JSON =  ["val1":val1 as Int, "val2":val2 as Int]
                let str = json.description
                let data = str.dataUsingEncoding(NSUTF8StringEncoding)!
                if let file = NSFileHandle(forWritingAtPath:path) {
                    file.writeData(data)
            }
        }
   }

Answer 1

let file = "/settings.json" 无法在设备上运行。

您需要查看 NSBundle(我会在一两分钟内更新这篇文章，当我可以为您提供一些示例代码时)

目前我只有 objective c 代码——但它应该是一样的:

NSBundle* myBundle = [NSBundle bundleWithIdentifier:@"org.mitre.EGM96GeoidCalculator"];
NSString *path2 = [myBundle pathForResource:@"EGM96" ofType:@""];

你需要在 swift 中做的 - 等等是相似的(见这篇文章:Reading in a JSON File Using Swift)

if let path = NSBundle.mainBundle().pathForResource("test", ofType: "json")
{
    if let jsonData = NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe, error: nil)
    {
        if let jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(jsonData, options: NSJSONReadingOptions.MutableContainers, error: nil) as? NSDictionary
        {
            if let persons : NSArray = jsonResult["person"] as? NSArray
            {
                // Do stuff
            }
        }
     }
}

现在，如果您正在框架中做某事 - 或者您不想访问 mainBundle 而是访问带有框架标识符的包。