When I'm stopped at a break point in Xcode, I can see the value of NSString variables. How can I change them? I can change int or double variables, but not NSString.
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in 1987 we could easily use the equivalent of Xcode's "Edit Value..." in all the real debuggers. Now we are relegated to writing debugger code... Back to the Future...Cerniuk– Cerniuk2018-01-05 14:22:07 +00:00Commented Jan 5, 2018 at 14:22
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4 Answers
You can do this in the debug console. Say you have NSString* myVar. In the console, after (gdb), type set myVar = @"My new string". If you are using (lldb), then use the equivalent expression expr myVar = @"My new string" instead.
This may not show up correctly in the variables panel, but you can verify the value by entering po myVar into the console. Your code should pick up the new value.
For some great info about using expr, check out this StackOverflow post.
4 Comments
funroll
This doesn't work for me in XCode 4.3.1 using (lldb). I get errors about "reference to 'id' is ambiguous" and "1 errors parsing expression".
finneycanhelp
Using expr whateverVariable = @"55fc633a22570e2b7e00003b" worked for me.
Cerniuk
Its about the same amount of work to put: NSString * whateverVariable = @"55fc633a22570e2b7e00003b"; in the code itself. Sigh
You can but you have to call code from the debugger command prompt. For example, say you have a breakpoint fire off right after this line:
NSString *myString = @"My current string";
Then at the (gdb) prompt type:
call myString = @"My new string"
You can po myString before changing the string and after you change it to verify that it has changed.
Another example: Say you wanted to change a view controller's title. You can use the setter. *Note: dot notation is not supported at the debugger command line. For example let the view load and then set a breakpoint somewhere during the lifetime of your view controller. Then do this:
call (id)[self setTitle:@"New Title"]
Continue running the program and you should see your view controller's title update.
1 Comment
n8tr
my answer is old. You can actually do this now: po myString = @"my_new_string" and po self.title = @"New Title"
For NSError I am using this:
(lldb) expression aTempError = (NSError*)[[NSError alloc] initWithDomain:@"MANO" code:1 userInfo:nil]
Comments
(https://stackoverflow.com/users/1202867/n8tr) n8tr's comment from above shows how to do it. You just precede your assignment with "po " like so: po myString = @"my_new_string" and po self.title = @"New Title".
