objective-c 如何查看 NSError？

How can I view an NSError?

提问by nevan king

What's the best way to log an NSError?

登录 的最佳方式是NSError什么？

- (void)checkThing:(Thing *)thing withError:(NSError *)error {
    NSLog(@"Error: %@", error);
}

Gives me a nullmessage

给我null发消息

回答by James Raybould

Looking at the NSErrordocumentation tells me that you'll need to do something like:

查看NSError文档告诉我，您需要执行以下操作：

NSLog(@"%@",[error localizedDescription]);

This should then give you human readable output

这应该会给你人类可读的输出

回答by Peter Hosey

NSLog(@"Error: %@", error);

Gives me a null message

NSLog(@"Error: %@", error);

给我一个空消息

Then erroris nil, not an NSError instance.

然后error是nil，而不是 NSError 实例。

回答by Abizern

Here's a rough method I use to log errors while developing; (Not for Cocoa-touch)

这是我在开发时用来记录错误的粗略方法；（不适用于 Cocoa-touch）

// Execute the fetch request put the results into array
NSError *error = nil;
NSArray *resultArray = [moc executeFetchRequest:request error:&error];
if (resultArray == nil)
{
    // Diagnostic error handling
    NSAlert *anAlert = [NSAlert alertWithError:error];
    [anAlert runModal];
}

NSAlert takes care of displaying the error.

NSAlert 负责显示错误。