Groovy: Different behaviour observed using the eachWithIndex method - groovy

Question

I was doing a Groovy tutorial online there and after playing around with the code I observed some behaviour that I can't understand.
First I created a Map object like this:
def devMap = [:]
devMap = ['name':'Frankie', 'framework':'Grails', 'language':'Groovy']
devMap.put('lastName','Hollywood')
Then I called eachWithIndex to print out the values like so:
devMap.eachWithIndex { println "$it.key: $it.value"}
Which printed this to the console:
name: Frankie
framework: Grails
language: Groovy
lastName: Hollywood
But when I printed to the console from the eachWithIndex method like this using the arrow operator:
devMap.eachWithIndex { it, i -> println "$i: $it" }
The following got printed to the console:
0: name=Frankie
1: framework=Grails
2: language=Groovy
3: lastName=Hollywood
So what I can't understand is why the indexes got printed with the second statement and why there are = signs but no : signs between the key-value pairs?
Thanks.

Answer 1

When you use the no-arg version of eachWithIndex, it is the current entry in the Map. That means that it.key and it.value return what you expect.
When you use the two-arg version of eachWithIndex, again, it is the current entry in the Map and i is the current index. You're printing i, the index, and then since you are only printing it, you are getting the result of it.toString(), which formats the map entry as "${it.key}=${it.value}"

Answer 2

Your second example is equivalent to:
devMap.eachWithIndex { it, index -> println "$index: ${it.toString()}" }
where this shows that the toString() implementation uses the = syntax:
devMap.each { println it.toString() }
Note that this is closer to your goal (as I interpret it):
devMap.eachWithIndex { it, index -> println "$index: ${it.key}: ${it.value}" }