一个简单的代码，不知道如何调试

Question

In my BNRItem.m , I have implemented an class method:

#import "BNRItem.h"

@implementation BNRItem

+ (instancetype) randomItem {

    // Create an immutable array of three adjectives
    NSArray *randomAdjectiveList = @[@"Fluffy", @"Rusty", @"Shiny"];

    //three nouns
    NSArray *randomNounList = @[@"Bear", @"Spork", @"Mac"];

    //random number for 0 to 2
    //NOTE: NSInteger is not an object, but a type definition for "long"
    NSInteger adjectiveIndex = arc4random() % [randomAdjectiveList count];
    NSInteger nounIndex = arc4random() % [randomNounList count];

    NSString *randomName = [NSString stringWithFormat:@"%@ %@",
                            randomAdjectiveList[adjectiveIndex],
                            randomNounList[nounIndex]];

    int randomValue = arc4random() % 100;

    NSString *randomSerialNumber = [NSString stringWithFormat:@"%c%c%c%c%c",
                                    '0' + arc4random() % 10,
                                    'A' + arc4random() % 26,
                                    '0' + arc4random() % 10,
                                    'A' + arc4random() % 26,
                                    '0' + arc4random() % 10];


    BNRItem *newItem = [[self alloc] initWithItenName:randomName
                                          valueInDollars:randomValue
                                            serialNumber:randomSerialNumber];

    return newItem;

}

@end

In main.m, I try to call the class method to create new instance of BNRItem:

#import <Foundation/Foundation.h>
#import "BNRItem.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSMutableArray *items = [[NSMutableArray alloc] init];

        for (int i = 0; i < 10; i++) {
            //Thread 1: breakpoint 1.1
            BNRItem *item = [BNRItem randomItem];
            [items addObject:item];
        }

        for (BNRItem *item in items) {
            NSLog(@"%@", item);
        }

        //destroy the mutable array object
        items = nil;
    }
    return 0;
}

But, when I run my application, I ended up with the following thing which I don't understand how to debug, there is no error message, it just shows a breakpoint in code:

So, what is the problem in my code? How can I debug with this kind of situation? I mean, I am not only seeking for how to make my current code running, but also want to know how to debug with this situation? because the console doesn't tell much info about what is wrong in code.

Answer 1

Your application is running with breakpoint turned on. All you need to do is to click on the blue symbol (shown in below attached picture) and run it again. That symbol should turn white. You should then be good to go!

Answer 2

As others have said, you are hitting a breakpoint in your code. The blue arrow on line 17 in your screenshot is a breakpoint, and the fact that there is tick mark next to it and text in the right margin that says "Thread 1: breapoint..." tells you that you have hit a breakpoint.

This is a very useful debugging tool. You should learn how to use it. Clicking on the same spot on another line adds a breakpoint at that line. When you run your program, if that line of code is executed the debugger stops execution before the line is run and shows you the current value of the variables it things you need to see (variables that just changed, plus local variables.)

If you grab a blue breakpoint and drag away, it removes it. If you click on it it toggles between active and disabled.

There is also a debugger command line that lets you enter debugger commands to display the values of variables (And even execute code.)

For now, just drag the breakpoint away to delete it, but take the time to learn how to use breakpoints and the other features of the debugger. Truly, this is one of the most powerful features of an IDE and something you must learn how to do if you are going to progress beyond the beginner stage as a developer.