0

我想更新非可变字典中键“距离”的值，我有一个由从 json 读取的字典组成的数组，我需要更新应用程序中的所有距离值，能否请您提供示例代码那我该怎么做？

这是我创建这个数组的地方：

NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err];
    self.seachResult =[NSJSONSerialization JSONObjectWithData:responseData options:nil error:nil];

这是其中的示例信息：

2013-07-20 00:04:41.753 MyApp[61075:16a03] sorted array of dictionaries: (
    {
    cid = 2;
    distance = 0;
    image = "http://images.png";
    latitude = "48.245565";
    longitude = "16.342333";
    manual = "";
    movie = "http://jplayer.org/video/m4v/Big_Buck_Bunny_Trailer.m4v";
    pcode = 023942435228;
    pid = 1;
    pname = "example product";
    price = "12.00";
    qrcode = "";
    rid = 1;
    rname = "Example Retailer Name";
    sale = 0;
    "sale_percent" = 0;
    "sale_price" = "0.00";
    text = "here is text about sample product number 1...\nasdasdasda\nsdfsdfsd\nSdfsdf
},
    {
    cid = 1;
    distance = 0;
    image = "";
    latitude = "";
    longitude = "";
    manual = "";
    movie = "";
    pcode = 1;
    pid = 3;
    pname = "test product";
    price = "46.00";
    qrcode = "";
    rid = 2;
    rname = "";
    sale = 0;
    "sale_percent" = 0;
    "sale_price" = "35.00";
    text = "some text here...

},
    {
    cid = 2;
    distance = 0;
    image = "httpestImage";
    latitude = "48.245565";
    longitude = "16.342333";
    manual = "";
    movie = "";
    pcode = 1;
    pid = 2;
    pname = "sample product 2";
    price = "126.00";
    qrcode = "";
    rid = 1;
    rname = "Example Retailer Name";
    sale = 1;
    "sale_percent" = 20;
    "sale_price" = "99.99";
    text = "here is text about sample product number 2...\nblah blah blah\nasdasdasd\nASdasdas\nASdasdasd";
}
)

为了测试，我尝试了这个，但即使我无法更新这样一个简单字典的值：

NSMutableDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                      @"value1", @"key1", @"value2", @"key2", nil];
[dict setValue:@"test" forKey:@"key2"];

错误：

2013-07-20 00:46:08.086 NSdictionaryTest[61130:11303] * 由于未捕获的异常“NSUnknownKeyException”而终止应用程序，原因：“[<__NSDictionaryI 0x7556390> setValue:forUndefinedKey:]：此类不符合键值编码为关键 key2。* First throw call stack: (0x1c90012 0x10cde7e 0x1d18fb1 0xb79e41 0xafb5f8 0xafb0e7 0x2200 0xf31c7 0xf3232 0x423d5 0x4276f 0x42905 0x4b917 0xf96c 0x1094b 0x21cb5 0x22beb 0x14698 0x1bebdf9 0x1bebad0 0x1c05bf5 0x1c05962 0x1c36bb6 0x1c35f44 0x1c35e1b 0x1017a 0x11ffc 0x1e5d 0x1d85) libc++abi.dylib: terminate called throwing an exception

4

3 回答 3

2

如果要修改 JSONObjectWithData 返回的字典，请使用 NSJSONReadingMutableContainers 选项。这会导致该方法返回可变容器类。例如：

self.seachResult =[NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableContainers error:nil];
于 2013-07-19T22:22:28.237 回答
2

您需要使用不可变字典有什么特别的原因吗？

你可以使用NSMutableDictionary

我猜 self.seachResult 是你的 NSDictionary，你可以简单地将它声明为 NSMutableDictionary。

初始化它：

self.seachResult = [NSMutableDictionary dictionaryWithCapacity:10];
[self.seachResult addEntriesFromDictionary: NSJSONSerialization JSONObjectWithData:responseData options:nil error:nil]]; 
[self.seachResult setObject:YOUR_UPDATED_VALUE_HERE forKey:@"distance"];

此外，您还可以创建一个新的 NSMutableDictionary 并用非可变条目中的条目填充它，如下所示：

NSMutableDictionary *mutableSearchResults = [NSMutableDictionary dictionaryWithCapacity:[self.seachResult count]];
[mutableSearchResults addEntriesFromDictionary: self.seachResult];
[self.seachResult setObject:YOUR_UPDATED_VALUE_HERE forKey:@"distance"];

如果你想再次返回一个不可变的，你可以这样做：

[mutableSearchResults copy];

我希望它有所帮助。请注意，我只是在 SO 编辑器中输入了代码，所以我可能拼错了一些。

于 2013-07-19T22:28:23.950 回答
0

NSDictionary 是不可变的（创建后无法更改）。看看 NSMutableDictionary 代替。顺便说一句——从 NSDictionary 创建 NSMutableDictionary 很容易。

于 2013-07-19T22:19:02.383 回答