Problem with Vec using ink

Question

I'm trying to make some changes to the Flipper contract, trying to use a vector like the documentation say's it should be imported:

#[ink::contract]
pub mod flipper_plus {
    use ink::storage::Mapping;
    use ink::prelude::vec::Vec;

and during compilation got this errors:

error[E0432]: unresolved import `crate::flipper_plus::vec`
 --> /Users/pierina/Documents/rust_projects/flipper-contract/contracts/flipperPlus/src/lib.rs:7:30
  |
7 |     use crate::flipper_plus::vec::Vec;
  |                              ^^^ could not find `vec` in `flipper_plus`

error: cannot find macro `vec` in this scope
  --> /Users/pierina/Documents/rust_projects/flipper-contract/contracts/flipperPlus/src/lib.rs:33:26
   |
33 |                 history: vec![(caller, init_value, Self::env().block_timestamp())], 
   |                          ^^^

Here is my Cargo.toml:

[package]
name = "flipper_plus"
version = "0.1.0"
authors = [""]
edition = "2021"

[dependencies]
ink = { version = "4.0.0", default-features = false }

scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive"] }
scale-info = { version = "2.3", default-features = false, features = ["derive"], optional = true }

[lib]
name = "flipper_plus"
path = "src/lib.rs"
crate-type = [
    # Used for normal contract Wasm blobs.
    "cdylib",
]

[features]
default = ["std"]
std = [
    "ink/std",
    "scale/std",
    "scale-info/std"
]
ink-as-dependency = []

Answer 1

You only imported Vec. So, it could not find vec!.

And this error use crate::flipper_plus::vec::Vec;. It isn't the same as the code that you provided. use ink::prelude::vec::Vec;.

So, please update those imports correctly.

https://docs.rs/ink_prelude/4.1.0/ink_prelude/index.html

use ink::prelude::{vec, vec::Vec};

Answer 2

You need firstly add to your Cargo.toml following line:

ink_prelude = { version = "4.0.2", default-features = false }

and then you can use vec like:

use ink::prelude::{vec, vec::Vec};

Documentation: https://crates.io/crates/ink_prelude