# (More) helpful run-time error messages

**URL:** <https://www.ruby-forum.com/t/more-helpful-run-time-error-messages/261050>\
**Category:** Uncategorized\
**Created:** [March 2, 2021, 3:18pm UTC](https://www.ruby-forum.com/t/more-helpful-run-time-error-messages/261050 "2021-03-02T15:18:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![innersund](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/4da419/32.png) [@innersund](https://www.ruby-forum.com/u/innersund)\
**Post date:** [March 2, 2021, 3:18pm UTC](https://www.ruby-forum.com/t/more-helpful-run-time-error-messages/261050/1 "2021-03-02T15:18:58Z")

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I love Ruby, but the run-time error messages could be more helpful. An example: I have an array in 3 levels, and use map to transform the inner elements. Basically something like  
`ary=[1,2,3] # but actually 3 levels`  
`new_ary = ary.map { |n| n*fact }`  
resulting in the error message  
`TypeError (Array can't be coerced into Integer)`  
Because of the somewhat convoluted array structure I thought there was something wrong with the way I accessed the inner elements of ary. I struggled to find the error, until it dawned upon me that `fact`, coming from an external call, was an array and not a scalar. This would have been evident if the error message had included the name of the offending variable, like  
`TypeError (Array fact can't be coerced into Integer)`  
I would suppose that the name is available to the interpreter?

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<div class="post-metadata">

**Author:** ![pcl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ecae2f/32.png) [@pcl](https://www.ruby-forum.com/u/pcl)\
**Post date:** [March 2, 2021, 4:06pm UTC](https://www.ruby-forum.com/t/more-helpful-run-time-error-messages/261050/2 "2021-03-02T16:06:46Z")

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> [@innersund](#):
>
> I would suppose that the name is available to the interpreter?

I’m not sure. The \* operator would just get the values, and then it realises it has an Array not an Integer. You might need some kind of debugger to back out of that: ‘fact’ may not be a variable name, but a method call, or any arbitrarily complicated expression.

In irb and from command line, ruby does point me to the line and statement that the error comes up on:

```auto
Traceback (most recent call last):
	3: from test.rb:3:in `<main>'
	2: from test.rb:3:in `map'
	1: from test.rb:3:in `block in <main>'
test.rb:3:in `*': Array can't be coerced into Integer (TypeError)

```

So I can see _where_ the problem lies. Usually I end up putting print statements around that, to see if things are what I expect…

(I’m often tripping over problems like this with dynamic languages. They can be big time sinks in debugging.)