ios 如何从 NSError 获取更多有用的信息？
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How can I get more useful information from NSError?
提问by kevin young
I want to get some useful information from NSError.
If I print out [error userInfo], I get the following:
我想从NSError. 如果我打印出来[error userInfo]，我会得到以下信息：
{
NSFilePath = "/Users/apple/Library/Application Support/iPhone Simulator/5.1/Applications/08260B6A-4D65-48DF-ADD1-FFC8750081E8/Documents/abc";
NSUnderlyingError = "Error Domain=NSPOSIXErrorDomain Code=17 \"The operation couldn\U2019t be completed. File exists\"";
}
I want to show the last line : "File exists", but how can i pick it out?
我想显示最后一行：“文件存在”，但我怎样才能把它挑出来？
I tried:
我试过：
localizedDescription
localizedFailureReason
localizedRecoverySuggestion
localizedRecoveryOptions
recoveryAttempter
Non of them show "File exists".
他们都没有显示“文件存在”。
回答by kevin young
Finally, I follow code for perfect NSError print. Thanks @jbat100 and @Peter Warbo, I add a little bit on them code:
最后，我按照代码进行完美的 NSError 打印。感谢@jbat100 和@Peter Warbo，我在他们上面加了一点代码：
NSDictionary *userInfo = [error userInfo];
NSString *errorString = [[userInfo objectForKey:NSUnderlyingErrorKey] localizedDescription];
回答by Peter Warbo
How about:
怎么样：
NSDictionary *userInfo = [error userInfo];
NSString *error = [userInfo objectForKey:@"NSUnderlyingError"];
NSLog(@"The error is: %@", error);
回答by jbat100
If you look up the NSError documentation, it has a User info dictionary keyssection which has a constant defined as NSUnderlyingErrorKey (it also has a description for the keys).
如果您查找NSError 文档，它有一个User info dictionary keys部分，其中有一个定义为 NSUnderlyingErrorKey 的常量（它还具有键的描述）。
NSDictionary *userInfo = [error userInfo];
NSError *underlyingError = [userInfo objectForKey:NSUnderlyingErrorKey];
NSString *underlyingErrorDescription = [underlyingError localizedDescription];
回答by lansher1985
localizedRecoverySuggestion is very useful. You can get the JSON string from it:
localizedRecoverySuggestion 非常有用。您可以从中获取 JSON 字符串：
NSString *JSON = [[error userInfo] valueForKey:NSLocalizedRecoverySuggestionErrorKey] ;
NSError *aerror = nil;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData: [JSON dataUsingEncoding:NSUTF8StringEncoding]
options: NSJSONReadingMutableContainers
error: &aerror];
