Errors

Reading errors is most of what programming is… at least in my opinion. I found while I can read and write code, I become faster at making important decisions when I can decide the most important parts of an error message that are telling me what is wrong with the code. Here are some examples of what I have come across while making errors of GoLang and its code it caused.

invalid memory address or nil pointer

The Error

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
        panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x10e445c]

goroutine 7 [running]:
testing.tRunner.func1.2({0x10f5fe0, 0x11e83d0})
        /Users/addlema/.goenv/versions/1.17.1/src/testing/testing.go:1209 +0x24e
testing.tRunner.func1()
        /Users/addlema/.goenv/versions/1.17.1/src/testing/testing.go:1212 +0x218
panic({0x10f5fe0, 0x11e83d0})
        /Users/addlema/.goenv/versions/1.17.1/src/runtime/panic.go:1038 +0x215
personal-budget/module2.CreateBudget(...)
        /Users/addlema/src/github.com/golang-personal-budget-cli/module2/budget_2.go:81
personal-budget/module2.TestCreateValidBudgetAddsToReport(0xc0001304e0)
        /Users/addlema/src/github.com/golang-personal-budget-cli/module2/budget_2_test.go:70 +0x5c
testing.tRunner(0xc0001304e0, 0x1118490)
        /Users/addlema/.goenv/versions/1.17.1/src/testing/testing.go:1259 +0x102
created by testing.(*T).Run
        /Users/addlema/.goenv/versions/1.17.1/src/testing/testing.go:1306 +0x35a
FAIL    personal-budget/module2 0.693s
FAIL

I found some of the following things of this panic runtime error:

1. the path of the object and the function
2. the path of the file and the line number, which is 81
3. the way this function got called from the top to the bottom

personal-budget/module2.CreateBudget(...)
        /Users/addlema/src/github.com/golang-personal-budget-cli/module2/budget_2.go:81

The code that caused it

newBudget.Max = max

The fix is actually supposed to be this:

newBudget = &Budget{Max: max}

Which is settings a variable to be the Struct’s address and assigning the Max attribute with the value that is stored in max.