php - JSON 解析 --> Swift | JSON 写入中的顶级类型无效

Question

我正在尝试使用 Swift 从 PHP 文件中检索信息。我在网上看到我应该使用JSON解析(我认为它被称为)。所以我在网上搜索并找到了一些信息，导致我得到以下代码:

func dataOfJson(urlString: String) -> NSArray{
    let url = NSURL(string: urlString);
    if (url != nil)
    {
        let data = NSData(contentsOf: url as! URL);
        if (data != nil)
        {
            return try! JSONSerialization.data(withJSONObject: data as Any) as AnyObject! as! NSArray;
        }else{
            //return "Error -> Data is nil!";
            return try! JSONSerialization.data(withJSONObject: data as Any) as AnyObject! as! NSArray;
        }
    }else{
        return ["Error -> url is empty!"] as NSArray;
    }
}

我这样调用上面的函数:print(dataOfJson(urlString: "some url/test.php"));

我调用的 URL 包含以下 PHP 代码:

<?php   
header("Content-Type: application/json");
require "dbconnect.php";
global $connect;
$result = array();
$temp = array();

if ($connect){
    $fetch_data = mysqli_query($connect,"select * from dedi");

    while ( $row = $fetch_data->fetch_object() ){
        $temp = $row;
        array_push($result,$temp);
    }

    echo json_encode($result);
    return json_encode($result);
}
else{
    echo json_encode("Something went wrong");
    return json_encode("Something went wrong!");    
} 
mysqli_close(); ?>

遗憾的是，当我尝试运行该项目时，出现以下错误:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[NSJSONSerialization dataWithJSONObject:options:error:]: Invalid top-level type in JSON write'

我完全不知道如何修复它，是的，我在网上搜索并发现了类似的解决方案问题，但我无法理解这些问题，并且某些修复并没有改变任何内容......

Answer 1

documentation of NSJSONSerialization指出了 PHP 脚本中的 JSON 可能并不总是符合的一些要求:

An object that may be converted to JSON must have the following properties:

• The top level object is an NSArray or NSDictionary.
• All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
• All dictionary keys are instances of NSString.
• Numbers are not NaN or infinity.