DBI64

#![allow(unused)]
fn main() {
pub struct DBI64<T>
where 
    T: Packer + PrimaryValueInterface + Default,
{
    ///
    pub code: u64,
    ///
    pub scope: u64,
    ///
    pub table: u64,
    _marker: core::marker::PhantomData<T>,
}
}

DBI64 represents an on-chain key-value database with u64 as key and stores variable lengths of data.

New

#![allow(unused)]
fn main() {
pub fn new(code: Name, scope: Name, table: Name) -> Self
}

Creates a new DBI64 instance

Store

#![allow(unused)]
fn main() {
pub fn store(&self, key: u64,  value: &T, payer: Name) -> Iterator<T>
}

Store a value indexed by the key. payer specifies account to pay the RAM resources. VM throws an exception that can't catch by contract code if there is already a value with the key that exists in the database.

The following example code shows how to check if a value with the key already exists.

#![allow(unused)]
fn main() {
let it = db.find(key);
if !it.is_ok() {
    //create a new value
    //let value = ...
    db.store(key, &value, payer);
} else {
    let mut value = it.get_value();
    // modify value
    // ...
    db.update(it, &value, payer);
}
}

Find

#![allow(unused)]
fn main() {
pub fn find(&self, key: u64) -> Iterator<T>
}

Find value by primary key

Update

#![allow(unused)]
fn main() {
pub fn update(&self, iterator: &Iterator<T>, value: &T, payer: u64)
}

Update a value in the database. payer specifies account to pay the RAM resources. The related action in the transaction must contain the corresponding permission of the payer.

#![allow(unused)]
fn main() {
let it = db.find(key);
if !it.is_ok() {
    //create a new value
    //let value = ...
    db.store(key, &value, payer);
} else {
    let mut value = it.get_value();
    // modify value
    // ...
    db.update(it, &value, payer);
}
}

Examples

counter

token

Source Code

db.rs