understanding Xcode debugger var display

Question

newbie question: can anyone tip me to how to understand/interpret what is displayed in the debugger var pane?

Ex: I am passing an NSDictionary as a method param. I set a breakpoint so I can examine the values in the dictionary. The image below (if it comes through..) shows the expanded view of this var in the debugger. It correctly reports that it contains 3 name/value pairs but as I expand all the sections, I simply can not find where these are stored.

Do I have to create local vars of these name/value pairs in order to view them when I want to check? I know I can use NSLog or printf but sometimes I just want a quick peek.

Answer 1

Right click the variable, click "Edit Summary Format" and type the following:

{(NSString*)[$VAR description]}:s

This replaces the GDB formatter for NSDictionary with a call to the more expensive description method.
That is, instead "x key/value pairs", you'll see the contents of the dictionary as produced by -[NSDictionary description].

This is the same as typing po dictionary in the console window. Or right clicking the variable and choosing "Print Description". Both of them call the description method of the object.

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If you are curious, you can find this formatter at /Developer/Library/Xcode/CustomDataViews/Foundation.plist under the key NSDictionary. What you type as replacement is saved in /Users/USERNAME/Library/Developer/Xcode/UserData/Debugger/CustomDataFormatters and will persist across runs until you delete that file.

A NSDictionary is really a class cluster and few people know the inside structure. At this point you ain't going to find much use for that debugger tree.