Try to transfer tokens to one of the account declared in remaining_accounts list.
Here's the way I create CpiContext:
let cpi_context = CpiContext::new(ctx.accounts.token_program.to_account_info(),
Transfer {
from: ctx.accounts.account_x.to_account_info(),
to: ctx.remaining_accounts.first().unwrap().to_account_info(),
authority: ctx.accounts.owner.to_account_info().clone()
});
I got error related to CpiContext lifetime mismatch. Exact log error: lifetime mismatch ...but data from ctx flows into ctx here.
Why I want to use remaining accounts to transfer tokens? This transfer is optional depending on whether user decides to pass the account (referral links/affiliation). Other methods than passing account as remaining accounts to implement the optional transfer will be also highly appreciated.
Make sure that you help out Rust's lifetime inference in your instruction:
pub fn your_instruction<'info>(ctx: Context<'_, '_, '_, 'info, YourContext<'info>>, ...)
Related
Considering that
get_esdt_token_data(address: &ManagedAddress, token_id: &TokenIdentifier, nonce: u64) -> EsdtTokenData<Self::Api>
always returns an EsdtTokenData rather than an option. What will this object look like if the address does not own the specified token?
The execution will fail as the VM will not return anything to the smart contract if it doesn't find the token.
The typical usage for this function is to get the data for the payment tokens the smart contract receives from the caller. If you're trying to use it freely, you might get into this situation, so this type of "free" usage is not really advised.
I have a NEAR application in which most of the methods do not transfer any tokens. Users go through the standard login flow with NEAR wallet, have their 0.25N allowance for gas, and then interact with the application.
I now have a new end-point that I want to be callable from the front-end, which expects the user to pay an amount significantly exceeding 0.25N:
#[payable]
pub fn buy_stuff() {
When I use the standard near-api-js way to call it:
window.contract.buy_stuff({}, undefined, price).then(m => window.location.href='/');
it fails, because it tries to spend the price from the allowance of the aceess key logged in, which it doesn't have -- it naturally only has 0.25N it has for gas.
The specific error is "Access Key {account_id}:{public_key} does not have enough balance 247864837491516400000000 for transaction costing 5004231023352653388973496"
What I want instead is to get the user redirected to the wallet, and authorize this particular transaction using their full access key in the wallet. Is there a way to do that with near-api-js?
It looks like the issue is that the contract API doesn't consider a wallet redirect. One reason might be the initialization of the contract API.
In order for a contract API to be able to redirect to a wallet, the initialization should be done with the ConnectedWalletAccount. It can be done using the following code:
const nearConnection = await nearAPI.connect(...);
const walletConnection = new nearAPI.WalletConnection(
nearConnection,
ContractName
);
const contract = new nearAPI.Contract(
walletConnection.account(),
ContractName,
{
viewMethods: [...],
changeMethods: [...],
}
);
Can any one please help me on the transaction/operation types in Near where value/near is involved.I have seen multiple operation types like transfer , draw etc
There are only 7 native action kinds in NEAR Protocol:
Transfer (deposit gets transferred from a signer to a receiver account)
CreateAccount
DeleteAccount (the remaining funds on an account are transferred to the beneficiary account id)
CallFunction (tokens can be deposited [attached] to the function call, e.g. draw method expects some tokens attached)
AddKey
DeleteKey
I want to delete the current contract and burn its NEAR balance when a condition is triggered.
Here's the Solidity version:
selfdestruct(address(0));
I found Promise::delete_account in the Rust SDK but it has a beneficiary_address field. Ideally the funds should be gone forever and not transferred to an owned address.
Promise::new(env::current_account_id()).delete_account(beneficiary_address);
address(0) is address 0x0, a black hole address used to burn Ether.
Currently there is no API to burn NEAR tokens directly. One workaround is to set the beneficiary account id to system. system is an account that can never be created and is used internally for refunds. When the beneficiary account does not exist, the tokens transferred through account deletion are automatically burnt.
I think that is like this:
#[payable]
pub fn burn() {
Promise::new("system".to_string()).transfer(env::attached_deposit());
}
First importing:
use near_sdk::{Promise};
I want to store all the blockchain data in offchain database.
rpc has a function called EXPERIMENTAL_changes, I was told that I can do that by http polling of this method but I am unable to find out how to use it.
http post https://rpc.testnet.near.org jsonrpc=2.0 id=dontcare method=EXPERIMENTAL_changes \ params:='{ "changes_type": "data_changes", "account_ids": ["guest-book.testnet"], "key_prefix_base64": "", "block_id": 19450732 }'
For example here the results give:
"change": { "account_id": "guest-book.testnet", "key_base64": "bTo6Mzk=", "value_base64": "eyJwcmVtaXVtIjpmYWxzZSwic2VuZGVyIjoiZmhyLnRlc3RuZXQiLCJ0ZXh0IjoiSGkifQ==" }
What is key_base64?
Decoding it to string gives m::39
What is m::39?
For example, I have the following state data in the rust structure.
pub struct Demo {
user_profile_map: TreeMap<u128, User>,
user_products_map: TreeMap<u128, UnorderedSet<u128>>, // (user_id, set<product_id>)
product_reviews_map: TreeMap<u128, UnorderedSet<u128>>, // (product_id, set<review_id>)
product_check_bounty: LookupMap<u128, Vector<u64>>
}
How to know anything gets changed in these variables?
Will I have to check every block id for the point the contract is deployed, to know where there is the change?
I want to store all the blockchain data in offchain database.
If so, I recommend you take a look at the Indexer Framework, which allows you to get a stream of blocks and handle them. We use it to build Indexer for Wallet (keeps track of every added and deleted access key, and stores those into Postgres) and Indexer for Explorer (keeps track of every block, chunk, transaction, receipt, execution outcome, state changes, accounts, and access keys, and stores all of that in Postgres)
What is m::39?
Contracts in NEAR Protocol have access to the key-value storage (state), so at the lowest-level, you operate with key-value operations (NEAR SDK for AssemblyScript defines Storage class with get and set operations, and NEAR SDK for Rust has storage_read and storage_write calls to preserve data).
Guest Book example uses a high-level abstraction called PersistentVector, which automatically reads and writes its records from/to NEAR key-value storage (state). As you can see:
export const messages = new PersistentVector<PostedMessage>("m");
Guest Book defines the messages to be stored in the storage with m prefix, hense you see m::39, which basically means it is messages[39] stored in the key-value storage.
What is key_base64?
As key-value storage implies, the data is stored and accessed by keys, and the key can be binary, so base64 encoding is used to enable JSON-RPC API users with a way to query those binary keys as well (there is no way you can pass a raw binary blob in JSON).
How to know anything gets changed in these variables? Will I have to check every block id for the point the contract is deployed, to know where there is the change?
Correct, you need to follow every block, and check the changes. That is why we have built the Indexer Framework in order to enable community building services on top of that (we chose to build applications Indexer for Wallet and Indexer for Explorer, but others may decide to build GraphQL service like TheGraph)