<h1 align="center">How to Use Blockchain & Block API in Smart Contract</h1>
<p align="center" class="version">Version 0.1</p>
1. Introduction
There are five major APIs in Ontology smart contract and blockchain API is one of them. Blockchain API supports basic blockchain query and operation such as getting current block height. Block API supports query about transaction. More API will be available in the future.
For more details, you can view the API-doc and the source code here.
2. How to use Blockchain API
2.1 Import
from boa.interop.System.Blockchain import GetHeight, GetHeader, GetBlock, GetTransactionHeight, GetContract, GetTransactionByHash
2.2 Blockchain API
GetHeight
from boa.interop.System.Runtime import Notify
from boa.interop.System.Blockchain import GetHeight
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
height=GetHeight()
Notify(height)
return height
GetHeader
from boa.interop.System.Runtime import Notify
from boa.interop.System.Blockchain import GetHeader
def Main(operation, args):
if operation == 'demo':
block_height=args[0]
return demo(block_height)
return False
def demo(block_height):
header=GetHeader(block_height)
Notify(header)
return header
GetTransactionByHash
from boa.interop.System.Blockchain import GetHeight, GetHeader, GetBlock, GetTransactionHeight, GetContract, GetTransactionByHash
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
# tx_hash="9f270aa3a4c13c46891ff0e1a2bdb3ea0525669d414994aadf2606734d0c89c1"
tx_hash=bytearray(b"\xc1\x89\x0c\x4d\x73\x06\x26\xdf\xaa\x94\x49\x41\x9d\x66\x25\x05\xea\xb3\xbd\xa2\xe1\xf0\x1f\x89\x46\x3c\xc1\xa4\xa3\x0a\x27\x9f")
tx=GetTransactionByHash(tx_hash)
return tx
GetTransactionHeight
from boa.interop.System.Blockchain import GetHeight, GetHeader, GetBlock, GetTransactionHeight, GetContract, GetTransactionByHash
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
# tx_hash="9f270aa3a4c13c46891ff0e1a2bdb3ea0525669d414994aadf2606734d0c89c1"
tx_hash=bytearray(b"\xc1\x89\x0c\x4d\x73\x06\x26\xdf\xaa\x94\x49\x41\x9d\x66\x25\x05\xea\xb3\xbd\xa2\xe1\xf0\x1f\x89\x46\x3c\xc1\xa4\xa3\x0a\x27\x9f")
height=GetTransactionHeight(tx_hash)
return height # the return value 1018 is a hex number. We can get 6160 after transferring it.
GetContract
from boa.interop.System.Blockchain import GetHeight, GetHeader, GetBlock, GetTransactionHeight, GetContract, GetTransactionByHash
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
# contract_hash="d81a75a5ff9b95effa91239ff0bb3232219698fa"
contract_hash=bytearray(b"\xfa\x98\x96\x21\x32\x32\xbb\xf0\x9f\x23\x91\xfa\xef\x95\x9b\xff\xa5\x75\x1a\xd8")
contract=GetContract(contract_hash)
return contract
GetBlock
There are two ways to get block.
- Get block by height
from boa.interop.System.Blockchain import GetHeight, GetHeader, GetBlock, GetTransactionHeight, GetContract, GetTransactionByHash
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
block=GetBlock(1408)
return block
- Get block by block hash
You need to reverse block hash of hex string first and then transfer it to byte array. For example, if block hash of hex string is e40315e22fc30b4648e3546d33927317f7175dc4c866ea443077798240c5e016, reversing it to 16e0c5408279773044ea66c8c45d17f7177392336d54e348460bc32fe21503e4 and then transferring it to \x16\xe0\xc5\x40\x82\x79\x77\x30\x44\xea\x66\xc8\xc4\x5d\x17\xf7\x17\x73\x92\x33\x6d\x54\xe3\x48\x46\x0b\xc3\x2f\xe2\x15\x03\xe4. It is an important procedure. Otherwise, you would get an error which indicates that there is no block of this block hash.
from boa.interop.System.Blockchain import GetHeight, GetHeader, GetBlock, GetTransactionHeight, GetContract, GetTransactionByHash
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
block_hash=bytearray(b'\x16\xe0\xc5\x40\x82\x79\x77\x30\x44\xea\x66\xc8\xc4\x5d\x17\xf7\x17\x73\x92\x33\x6d\x54\xe3\x48\x46\x0b\xc3\x2f\xe2\x15\x03\xe4')
block=GetBlock(block_hash)
return block
3. How to use Block API
3.1 Import
from boa.interop.System.Block import GetTransactions, GetTransactionCount, GetTransactionByIndex
3.2 Block API
GetTransactionCount
from boa.interop.System.Blockchain import GetBlock
from boa.interop.System.Block import GetTransactionCount
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
block=GetBlock(1408)
count=GetTransactionCount(block)
return count
GetTransactions
from boa.interop.System.Blockchain import GetBlock
from boa.interop.System.Block import GetTransactionCount
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
block=GetBlock(1408)
txs=GetTransactions(block)
return txs
GetTransactionByIndex
from boa.interop.System.Blockchain import GetBlock
from boa.interop.System.Block import GetTransactionByIndex
def Main(operation):
if operation == 'demo':
return demo()
return False
def demo():
block=GetBlock(1408)
tx=GetTransactionByIndex(block,0) # index starts from 0.
return tx
4. Contributing
Please feel free to give any suggestion and help us make video better!
Contact: Yue Zhao
Wechat: 16621171248
Email: messixaviinsta0303@163.com
