You can pass a Rust std::vec::Vec into your contract method transparently. The following code calls a Sway contract method which accepts a Vec<SomeStruct<u32>>.
let arg =vec![SomeStruct { a:0 }, SomeStruct { a:1 }];methods.struct_in_vec(arg.clone()).call().await?;
You can use a vector just like you would use any other type -- e.g. a [Vec<u32>; 2] or a SomeStruct<Vec<Bits256>> etc.
Returning vectors from contract methods is supported transparently, with the caveat that you cannot have them nested inside another type. This limitation is temporary.
let response = contract_methods.u8_in_vec(10).call().await?;assert_eq!(response.value, (0..10).collect::<Vec<_>>());
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Note: you can still interact with contracts containing methods that return vectors nested inside another type, just not interact with the methods themselves