cargo-contract cannot build using the "stable" channel. Switch to nightly

Question

I want to run and build contract by thia command :

Step 1: cargo contract new my_contract

Step 2: cargo contract build

when i want to run Step 2 and i faced this error :

ERROR: cargo-contract cannot build using the "stable" channel. Switch to nightly. See https://github.com/paritytech/cargo-contract#build-requires-the-nightly-toolchain

rustc Version :

    cargo 1.69.0-nightly (82c3bb79e 2023-02-04)
release: 1.69.0-nightly
commit-hash: 82c3bb79e3a19a5164e33819ef81bfc2c984bc56
commit-date: 2023-02-04
host: x86_64-unknown-linux-gnu
libgit2: 1.5.0 (sys:0.16.0 vendored)
libcurl: 7.86.0-DEV (sys:0.4.59+curl-7.86.0 vendored ssl:OpenSSL/1.1.1q)
os: Ubuntu 22.04 (jammy) [64-bit]

whats the problem ? how can i solve this ?

Answer 1

It depends on the cargo-contract version. Pre 2.0.0 versions of cargo-contract use the nightly toolchain of rust. You can get it with rustup toolchain add nightly and then build with cargo +nightly contract build. You can omit the +nightly if you set the nightly toolchain as default with rustup default nightly.

ink! contracts where version < 4.0.0 need to be built with cargo-contract version < 2.0.0, therefore also with the nightly toolchain.

ink! 4 contracts need to be built with cargo-contract version 2 and can be built with both the stable and nightly toolchain.