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#golang
Title
# golang
s

salmon-account-74572

02/26/2021, 8:00 PM
I know the answer is going to be "use `Apply`", but I'm having some trouble with the specifics. 🙂 I'm trying to get the IP address of an instance launched on EC2 as a string. So far I've tried 
ApplyT
and 
ApplyString
variations of this snippet:
Copy code
ipAddrList[0] = bastion.PrivateIp.ApplyString(func(ipAddr string) string {
	return string(ipAddr)
})
What am I missing?
👀 1
b

broad-dog-22463

02/26/2021, 8:05 PM
what error are you getting?
s

salmon-account-74572

02/26/2021, 8:17 PM
I haven't actually run it yet; I'm thinking it doesn't work because VS Code's linting is reporting this: 
cannot use bastion.PrivateIp.ApplyString((func(ipAddr string) string literal)) (value of type pulumi.StringOutput) as string value in assignment
b

broad-dog-22463

02/26/2021, 8:18 PM
we do this a lot in our examples
notice the use of sprintf in there so it's definitely strings
s

salmon-account-74572

02/26/2021, 8:42 PM
It's not just VS Code...I just ran 
pulumi preview
and it reported the same error ("cannot use bastion.PrivateIp.OutputState.ApplyString(func literal) (type pulumi.StringOutput) as type string in assignment")
b

broad-dog-22463

02/26/2021, 9:03 PM
@billowy-army-68599 any thoughts on what I’ve missed here?
b

billowy-army-68599

02/26/2021, 9:08 PM
what is 
ipAddrList[0]
as a type?
can you show me the rest of your code? are you trying to build an array?
l

lemon-agent-27707

02/26/2021, 9:21 PM
From the error it sounds like 
ipAddrList
is a 
[]string
and you are trying to assign a 
pulumi.StringOutput
to one of it's elements which would not work. If you share a full code snippet with context I'm sure we can get something working.
b

billowy-army-68599

02/26/2021, 9:22 PM
yeah that was my thought too 🙂
s

salmon-account-74572

02/26/2021, 10:03 PM
You are spot on. I am trying to launch a group of instances and collect their IP addresses in an array that I can iterate over to write the IP addresses out to a file.
Taking a break for family for a bit, but I'll post more code for context later.
Here's a bit more code for context:
Copy code
// Launch an EC2 instance to serve as bastion host
		bastion, err := ec2.NewInstance(ctx, "bastion", &ec2.InstanceArgs{
			Ami:                      pulumi.String(amiID.Id),
			InstanceType:             pulumi.String("t2.small"),
			AssociatePublicIpAddress: pulumi.Bool(true),
			KeyName:                  pulumi.String("ssh_key_name"),
			SubnetId:                 pulumi.String(subnets.Ids[0]),
			VpcSecurityGroupIds:      pulumi.StringArray{bastionSecGrp.ID()},
			Tags: pulumi.StringMap{
				"Name": pulumi.String("ans-int-bastion"),
			},
		})
		if err != nil {
			log.Printf("error launching bastion instance: %s", err.Error())
		}

		// Get IP address of bastion as a string
		ipAddrList[0] = bastion.PrivateIp.ApplyString(func(s string) string {
			return fmt.Sprintf("%s", s)
		})
The ultimate goal---and perhaps I'm going about this the wrong way---is to get Pulumi to write out the IP addresses of the instances it launched into a file that could be used with something like Ansible. My thought process was that I'd gather the IP addresses as elements in a string array, then write the array elements to a file.
l

lemon-agent-27707

02/27/2021, 3:28 PM
If you don't need the file as a part of your program, you can just write it in an apply: https://gist.github.com/EvanBoyle/827ef2192cc878c7f708a4e612d2f2c0
s

salmon-account-74572

02/28/2021, 7:53 PM
Hmm...OK, I might be able to make that work. I'm assuming that the 
strings.Join
wouldn't be needed if I wanted each element on a separate line?
l

lemon-agent-27707

02/28/2021, 9:23 PM
strings.Join
was just the way I chose to do string formatting for example purposes
👍🏻 1
s

salmon-account-74572

03/01/2021, 2:50 PM
I moved to a slightly different model; relevant code is here: https://gist.github.com/scottslowe/bc023d3ea10b2cb22f59f7e295657f23 It successfully writes a value to the inventory file, but it isn't the IP address (I'm guessing it's some sort of string representation of the Output). I experimented with an 
ApplyString
function (see line 53 of the gist) but it doesn't seem to work.
l

lemon-agent-27707

03/01/2021, 3:38 PM
ApplyString
returns another Output which is why you are seeing this behavior. You'll need to do any printing from within an apply.
s

salmon-account-74572

03/01/2021, 3:46 PM
OK
Something like this, perhaps?
Copy code
tmp := bastion.PrivateIp.ApplyT(func(v string) string {
			res := v
			fmt.Fprintln(f, v)
			return res
		})
Well, that didn't work (file is empty).
Maybe I should switch to using the Automation API, since then stack outputs are just "ordinary" data types.
l

lemon-agent-27707

03/01/2021, 4:09 PM
Maybe I should switch to using the Automation API,
Using automation api would definitely make it pretty easy to take stack outputs and write them to a file.
s

salmon-account-74572

03/01/2021, 4:47 PM
I did put in a 
ctx.Export
statement (per your gist), but the file was still empty. I think I'm just going to rewrite it using the Automation API.
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