Understanding Terraform for_each loop iteration - terraform

Question

I am learning terraform and trying to understand the for_each loop iteration in terraform.
I am iterating through a loop for creating RGs in Azure cloud and what I want to understand is the difference between accessing the value of an instance using . or [""].
So for example, below is my tfvar file:
resource_groups = {
resource_group_1 = {
name = "terraform-apply-1"
location = "eastus2"
tags = {
created_by = "vivek89#test.com"
}
},
resource_group_2 = {
name = "terraform-apply-2"
location = "eastus2"
tags = {
created_by = "vivek89#test.com"
}
},
resource_group_3 = {
name = "terraform-apply-3"
location = "eastus2"
tags = {
created_by = "vivek89#test.com"
contact_dl = "vivek89#test.com"
}
}
}
and below is my terraform main.tf file:
resource "azurerm_resource_group" "terraformRG" {
for_each = var.resource_groups
name = each.value.name
location = each.value.location
tags = each.value.tags
}
I am confused with the expression in for_each in RG creation block. Both the below codes works and create RGs:
name = each.value.name
name = each.value["name"]
I want to understand the difference between the two and which one is correct.

Answer 1

They are equivalent as explained in the docs:
Map/object attributes with names that are valid identifiers can also be accessed using the dot-separated attribute notation, like local.object.attrname. In cases where a map might contain arbitrary user-specified keys, we recommend using only the square-bracket index notation (local.map["keyname"]).
The main difference is that dot notation requires key attributes to be valid identifiers. In contrast, the square-bracket notation works with any identifiers.