I'm trying to get better at using the debugger rather than just always printing my debugging message out via NSLog. This morning I thought I had a great use for it - to find how the changed values of a KVO dictionary. But when I set a breakpoint just after the appropriate code and ran with debugging on, all I saw in the debugger was this in the summary:
{(int)[$VAR count]} key/value pairs
and expanding the item never gets to any key or value.
But when I print out the "change" dictionary via NSLog I get the key and the value:
[timestamp] appName[3643:707] observeValueForKeyPath new filePath change: {
kind = 1;
new = foo;
I guess I have two questions:
Is there a way to get dictionary keys and values with the Xcode debugger?
Is there a set of rules of thumb for using the debugger vs printing log messages?
I'm (still) using Xcode 3.2.6.
Thanks!
EDIT: I realize that "foo" is not a valid file path. At this point I'm still testing sending a value around via KVO.
Set a breakpoint on the spot you want to check the value of the variable and run your application. When the breakpoint gets tripped put your mouse over the variable in the debugger. A little popup should come up, move your mouse over the arrows on the left side and another menu should popup. Click on "Print Description" and it should display something similar to a log in the console.
It is just a case by case method but a lot of it is just personal preference. You will just have to find what works for you.
If I am going to check a variable a lot at a one specific point, I will go with a log. It is usually the quickest way to see if something is working right
If I am checking how a part of the code affects a variable I will use the debugger and step through the code. It is also useful for checking the values of lots of variables in a section of code.
You can using a future set, which defenetely working in Xcode4
When u setup breakpoint, where is a option to don't stop execution of program and write to log anything what u want.
I'm not sure if it working well in Xcode 3 bcs I familiar with 4 but here is work.
Related
We have a customized mail template where we can set values of a parameter in mail preference.
After getting upgraded to Notes 9, when the parameter is set to Automatic it's working fine, but when another value is selected below thing happens (It was working fine in previous versions of Notes..):
After opening any external email, after double clicking on the mail body to edit.. notes is getting crashed.
I have two questions :
I see for external emails the control is going from querymodechange to queryclose while editing. Does it always happen?
I debugged the whole thing. Surprisingly it works in debug mode..no notes crash!!
Any help would be much appreciated !!!
This is why customizing the mail template is rarely recommended. There are interactions and dependencies between the code in the template and the Notes client, and it's very hard to debug. Since you haven't shown any of your customized code, I don't think anybody is going to be able to help you. I would recommend removing your customization code one piece at a time until it no longer crashes. Then you'll have an idea of what's triggering it, and you can try a different approach.
When Notes crashes, it dumps some diagnostics in the data/IBM_TECHNICAL_SUPPORT directory, notably the file console.log
You could review it and post here the lines pertaining to the crash.
Also, what was the previous version of Notes ?
To target the offending code line, you can use that old, dirty and tedious trick : add the folling line at the top of the QueryClose event, and move it down until you no longer see the result. Then post the context.
print now & "so far so good"
I'm not sure if this is possible. Here is an example situation:
Something is printing to my console and I don't know where it is coming from in the code. I did a quick search using the Finder in Xcode on terms such as 'NSLog' and 'print'. Nothing relevant came up.
Is there any quick way that Xcode has of finding where the source of the output is coming from ?
Kind of like when you right click on a method and you have all the options of exploring different parts of the code associated with that method.
Also: are there other functions that print besides NSLog and print?
Thanks so much!
Try running in the debugger, with breakpoints set on printf, NSLog, etc. When you hit a breakpoint do a backtrace (bt) to see where it's being called from
There's a plugin LinkedLog for that. You replace all NSLogs with LLogs and then will be able to just tap on link in Xcode's console to get to the line caused it to appear.
Didn't try it myself, but definitely will.
I am following the Stanford University iOS development course on iTunes U.
In one of the demos (that I have been trying to follow), there is this code that loads the property list from an NSURL and returns it as NSMutableDictionary.
-(NSMutableDictionary *) words
{
NSURL *wordsURL=[NSURL URLWithString:#"http://cs193p.stanford.edu/vocabwords.txt"];
words=[[NSMutableDictionary dictionaryWithContentsOfURL:wordsURL] retain];
return words;
}
The application is successfully built, but at runtime it gives the following error and gets stuck:
I can't figure out what the problem is. Can you please help?
You're stopped at a breakpoint. That's a debugging tool, not an error. See the blue arrow/tab in the left margin, where the line numbers are? Drag that away and drop it anywhere (you'll see a "poof") to remove it, then run your project again.
You can also deactivate all breakpoints by typing ⌘-Y, the key equivalent for the menu item Debug>Deactivate Breakpoints, or you can view all your breakpoints in the Breakpoint Navigator (hit ⌘-6).
When execution stops like this, you can continue from the breakpoint, either by typing continue at the debugger prompt in the Console:
(lldb) continue
Or hitting the "Play" button in the debugger controls. You can also type Control-⌘-Y, which is the equivalent for the menu item Debug>Continue.
This isn't an error. You just set a breakpoint (probably without knowing it).
Drag the little blue Chevron in the column at the left out of the way. You will see it disappear and go poof, and then you can rebuild your app and you should see it run properly.
Now, that said, I think there are some memory management mistakes in your code, but we can return to those later. ;-)
The program is stopping because you have a breakpoint.. That's the blue arrow on the left of the code. Right-click it and delete.
I am following the Stanford University iOS development course on iTunes U.
In one of the demos (that I have been trying to follow), there is this code that loads the property list from an NSURL and returns it as NSMutableDictionary.
-(NSMutableDictionary *) words
{
NSURL *wordsURL=[NSURL URLWithString:#"http://cs193p.stanford.edu/vocabwords.txt"];
words=[[NSMutableDictionary dictionaryWithContentsOfURL:wordsURL] retain];
return words;
}
The application is successfully built, but at runtime it gives the following error and gets stuck:
I can't figure out what the problem is. Can you please help?
You're stopped at a breakpoint. That's a debugging tool, not an error. See the blue arrow/tab in the left margin, where the line numbers are? Drag that away and drop it anywhere (you'll see a "poof") to remove it, then run your project again.
You can also deactivate all breakpoints by typing ⌘-Y, the key equivalent for the menu item Debug>Deactivate Breakpoints, or you can view all your breakpoints in the Breakpoint Navigator (hit ⌘-6).
When execution stops like this, you can continue from the breakpoint, either by typing continue at the debugger prompt in the Console:
(lldb) continue
Or hitting the "Play" button in the debugger controls. You can also type Control-⌘-Y, which is the equivalent for the menu item Debug>Continue.
This isn't an error. You just set a breakpoint (probably without knowing it).
Drag the little blue Chevron in the column at the left out of the way. You will see it disappear and go poof, and then you can rebuild your app and you should see it run properly.
Now, that said, I think there are some memory management mistakes in your code, but we can return to those later. ;-)
The program is stopping because you have a breakpoint.. That's the blue arrow on the left of the code. Right-click it and delete.
I set a breakpoint immediately following these lines:
NSInteger index = [self.aCombobox indexOfSelectedItem];
NSString *nameSelected = [self.names objectAtIndex:index];
If I then roll the mouse over nameSelected, it shows a value of “nil.” And if I type “po nameSelected” in the debugger console, it says the string “does not appear to point to a valid object.”
So I added an NSLog to print nameSelected, which duly printed the string. And, once debugger is below the NSLog line, if I roll the mouse over nameSelected, it shows the correct value.
Is there some reason why the debugger behaves this way? It makes it harder to identify where the real problem is.
Me (and millions of other iOS developers) do this all the time and have no issues. Though it seems a stupid query, have you made modifications to the source while debugging (specifically, added lines of code)? If so, the debugger is still pointing to line X from the .o file while your source is out of sync.
The real answer is Tommy's comment to this old question of mine. It was a Xcode newby mistake. Sorry to have left this hang out there so long,
Actually, our experience is that the iOS enabled GDB is buggy as anything. We've observed these kinds of bugs quite often.
There might be a solution, but most of the time we just sucked it up and resorted to NSLog Debugging.