How to have PDA space size depending on instruction argument

Question

I'm using anchor, so I define the space attribute in the Accounts struct, is there a way to make it depend on the instruction arg ?

It's for a PDA storing a string, and I don't know string length before the instruction is called. I can define a max length and allocate space for the max length but it's not very clean

Answer 1

Found out you can use the #[instruction] macro, to use the args you're waiting for. Also the anchor docs says that the space needed for a String is 4 + length of string in bytes. So i'd do something like that

#[derive(Accounts)]
#[instruction(content: String)]
pub struct InstructionExample {
    #[account(init, space: 8 + usize::from(4 + content.len())]
    pub pda_account: Account

}