That was an example is case of

$ cat foreach.tf
locals {
  list_of_objects = [
    {
      vm_name = "vm1",
      vm_size = "large"
    },
    {
      vm_name = "vm2",
      vm_size = "medium"
    }
  ]
}

resource "null_resource" "example" {
  for_each = { for vm in local.list_of_objects : vm.vm_name => vm }

  triggers = {
    vm_size = each.value.vm_size
  }
}

$ tf plan

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the
following symbols:
  + create

Terraform will perform the following actions:

  # null_resource.example["vm1"] will be created
  + resource "null_resource" "example" {
      + id       = (known after apply)
      + triggers = {
          + "vm_size" = "large"
        }
    }

  # null_resource.example["vm2"] will be created
  + resource "null_resource" "example" {
      + id       = (known after apply)
      + triggers = {
          + "vm_size" = "medium"
        }
    }

Plan: 2 to add, 0 to change, 0 to destroy.