How to fix Error: Invalid each attribute - The each object does not have an attribute named id in Terraform

resource "aws_instance" "example" {
  for_each = var.instances

  ami           = each.id          # ERROR: 'each' has no 'id' attribute
  instance_type = each.name        # ERROR: 'each' has no 'name' attribute
}

resource "aws_instance" "example" {
  for_each = var.instances

  ami           = each.value.ami
  instance_type = each.value.instance_type

  tags = {
    Name = each.key  # Use the key for naming
  }
}

variable "instances" {
  type = map(object({
    ami           = string
    instance_type = string
  }))
  default = {
    web = {
      ami           = "ami-12345"
      instance_type = "t2.micro"
    }
    db = {
      ami           = "ami-67890"
      instance_type = "t2.small"
    }
  }
}

resource "aws_instance" "example" {
  for_each = var.instances

  ami           = each.value.ami              # Access nested properties through 'value'
  instance_type = each.value.instance_type
  tags = {
    Name = each.key                           # 'key' is "web" or "db"
  }
}

variable "availability_zones" {
  type    = set(string)
  default = ["us-east-1a", "us-east-1b", "us-east-1c"]
}

resource "aws_subnet" "example" {
  for_each = var.availability_zones

  availability_zone = each.value    # 'value' is the zone string directly
  vpc_id            = aws_vpc.main.id

  tags = {
    Name = "subnet-${each.key}"    # 'key' is auto-generated index for sets
  }
}

output "debug_instances" {
  value = var.instances
}

for_each = {
  "web-1" = { size = "t2.micro", az = "us-east-1a" }
  "web-2" = { size = "t2.micro", az = "us-east-1b" }
}

instance_type = each.value.size    # Not each.instance_type or each.size
tags = { Name = each.key }         # 'web-1' or 'web-2'

for_each = {
  "web" = "ami-12345"
  "db"  = "ami-67890"
}

ami = each.value    # Not each.ami or each.key

# Instead of for_each = var.my_list (which fails for non-sets/maps)
for_each = { for idx, item in var.my_list : idx => item }

# Access the item through each.value
resource_name = each.value.name    # Not each.name or each.id

# WRONG - count attributes don't work with for_each
each.id          # ❌ Doesn't exist
each.index       # ❌ Doesn't exist (use count.index with count, not for_each)
each.count       # ❌ Doesn't exist

# CORRECT - only for_each attributes
each.key         # ✅ The map key
each.value       # ✅ The map value

# ❌ Wrong
for_each = toset(["web", "db", "cache"])
resource "aws_security_group" "example" {
  name = each.id
}

# ✅ Correct
for_each = toset(["web", "db", "cache"])
resource "aws_security_group" "example" {
  name = each.value
}

# ❌ Wrong - trying to access nested property directly
for_each = var.instances
instance_type = each.instance_type

# ✅ Correct - use each.value then the property
for_each = var.instances
instance_type = each.value.instance_type

# ❌ Wrong
for_each = { a = "value1", b = "value2" }
output_name = each.value    # When you meant the key

# ✅ Correct
for_each = { a = "value1", b = "value2" }
output_name = each.key      # If you want the key (a or b)
output_data = each.value    # If you want the value (value1 or value2)

# ❌ Wrong - lists are not supported directly by for_each
for_each = ["item1", "item2", "item3"]

# ✅ Correct - convert to set or map
for_each = toset(["item1", "item2", "item3"])
# OR
for_each = { for idx, item in ["item1", "item2", "item3"] : idx => item }

variable "my_resources" {
  type = any  # Temporary - use 'any' to accept any structure
}

output "debug_for_each" {
  value = var.my_resources
}

output "debug_for_each_type" {
  value = "Type check: ${jsonencode(var.my_resources)}"
}

resource "aws_instance" "example" {
  for_each = var.my_resources

  # Debug output for each iteration
  tags = {
    DebugKey   = each.key
    DebugValue = jsonencode(each.value)
  }
}

terraform plan

terraform console
> var.my_resources
> keys(var.my_resources)
> values(var.my_resources)

variable "subnet_config" {
  type = map(object({
    cidr_block = string
    az         = string
  }))
}

module "subnets" {
  for_each = var.subnet_config

  source = "./modules/subnet"

  name       = each.key              # Map key
  cidr_block = each.value.cidr_block # Nested property
  az         = each.value.az
}

# Access module outputs
output "subnet_ids" {
  value = { for k, v in module.subnets : k => v.subnet_id }
}

data "aws_ami" "example" {
  for_each = toset(["ubuntu", "amazon-linux", "centos"])

  filter {
    name   = "name"
    values = ["${each.value}-ami-*"]  # Use each.value directly
  }
}

output "ami_ids" {
  value = { for k, v in data.aws_ami.example : k => v.id }
}