# How to pass another canister as actor-constructor-argument?
**URL:** https://forum.dfinity.org/t/how-to-pass-another-canister-as-actor-constructor-argument/6233
**Category:** Developers
**Created:** [July 31, 2021, 6:03pm UTC](https://forum.dfinity.org/t/how-to-pass-another-canister-as-actor-constructor-argument/6233 "2021-07-31T18:03:45Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@shalexbas](https://forum.dfinity.org/u/shalexbas)
#### Post date: [July 31, 2021, 6:03pm UTC](https://forum.dfinity.org/t/how-to-pass-another-canister-as-actor-constructor-argument/6233/1 "2021-07-31T18:03:45Z")
Hey,
I played a bit with examples from [Payment-Channel-Example](https://github.com/DFINITY-Education/blockchain-and-cryptocurrency/blob/156c6cf4310e2eb836d0574b94f10c5838281689/src/Main.mo#L12)
There an [actor type](https://github.com/DFINITY-Education/blockchain-and-cryptocurrency/blob/156c6cf4310e2eb836d0574b94f10c5838281689/src/Types.mo#L33) is expected in constructor of the payment-actor. I have following questions:
- How to pass a different already existing canister as constructor argument?
- Is it possible to define a default constructor argument in dfx.json for an motoko actor?
Thanks
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### Author:  [@chenyan](https://forum.dfinity.org/u/chenyan)
#### Post date: [July 31, 2021, 7:04pm UTC](https://forum.dfinity.org/t/how-to-pass-another-canister-as-actor-constructor-argument/6233/2 "2021-07-31T19:04:45Z")
> [@shalexbas](#):
>
> (“rkp4c-7iaaa-aaaaa-aaaca-cai”)
Try `(principal "rkp4c-7iaaa-aaaaa-aaaca-cai")`
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### Author:  [@shalexbas](https://forum.dfinity.org/u/shalexbas)
#### Post date: [July 31, 2021, 7:29pm UTC](https://forum.dfinity.org/t/how-to-pass-another-canister-as-actor-constructor-argument/6233/3 "2021-07-31T19:29:20Z")
It didn’t work with “principal” but with “service”, Thanks!
Here is the working command for others: `dfx deploy paymentchannel --argument '(service "rkp4c-7iaaa-aaaaa-aaaca-cai")'`