Using the dAPI

Smart Contract and dApp development using Ontology's dAPI

The dAPI has been created to specifically facilitate dApp development. It supports browser (currently limited to Google Chrome) and mobile based dApp development (implemented using Cyano wallet that employs dAPI interface).

The mobile version of dAPI provides a limited number of the more significant interfaces only. The interfaces that query block transactions, or other interfaces that perform similar functions can directly invoke the explorer API interface. The dAPI interface set of the chrome plug-in is overall more comprehensive.

The code written in the two different environments is not mutually interchangeable currently. For compatibility related information, please refer: dapi-universal

This guides aims at providing a surface level introduction for some of the more commonly used interfaces- login, signature data, contract query, and contract invocation.

Note: The data returned by the dAPI interface is referred to as "Promise"

Configuration Process

dAPI Installation Flowchart

1. Installing dAPI

The first step is to install and set-up Ontology's dAPI package.

Ensure that Node.js is configured properly on your system. The installation process uses npm commands.

Chrome version-

npm install ontology-dapi

Mobile version-

npm install cyanobridge

2. Initialization

A contract must be initialized before it is invoked.

Chrome version

import {client} from 'ontology-dapi'
client.registerClient({})

Mobile version

import {client} from 'cyanobridge'
client.registerClient();

3. Login

There are two ways to implement the login mechanism in a dApp:

• Use the dAPI to directly fetch the user's account address or ONT ID. If the information can be retrieved successfully, it indicates the logged in state with respect to the dApp.

• The dApp back end generates a string and sends it to the front end, and the front end invokes the dAPI requesting it to assign a signature to it, and then returning it to the back end. If the back end can successfully verify this signature, the user can be considered to have logged in successfully. Next, the back end can issue access tokens to the user. This depends on the business logic of the dApp.

For more information on the method to implement back end signature verification, consider referring-

• Java SDK signature verification

• TypeScript SDK signature verification

Fetching Account Information or Identity

While fetching the account or identity information, the users working with the mobile version API may choose not to submit the dApp information and leave the fields empty.

Mobile version

import { client } from 'cyanobridge'

const params = {
    dappName: 'My dapp',
    dappIcon: '' // a URL that points to the dApp icon resource
}

try {
    const res = await client.api.asset.getAccount(params);
    const res = await client.api.identity.getIdentity(params);
    console.log(res)
} catch(err) {
    console.log(err)
}

Chrome version

account = await client.api.asset.getAccount()
res = await client.api.identity.getIdentity();

4. Data Signature

Here's some sample code to exemplify how the the signature mechanism can be carried out by the back end.

Mobile version

const params = {
    type: 'account',// account or identity that will sign the message
    dappName: 'My dapp', // dapp's name
    dappIcon: 'http://mydapp.com/icon.png', // the URL that points to the dapp's icon resource
    message: 'test message', // message sent from dapp that will be signed by native client
    expired: new Date('2019-01-01').getTime(), // expiry date of login
    callback: '' // callback url of dapp
}
let res;
try {
    res = await client.api.message.login(params);
    console.log(res)
}catch(err) {
    console.log(err)
}

Chrome version

const result = await client.api.message.signMessage({message});

5. Contract invocation

Contract invocations are mainly of two types: execution and pre-execution.

Pre-execution invocations normally involve using the contract's query interfaces, while the execution invocations directly use the contract itself. Pre-execution calls generally do not trigger the consensus mechanism. For example, in a game of rolling dice, a pre-execution invocation can query the result of a dice roll, and by the means of an execution invocation the specific method of a dice roll can be fetched.

Execution invocation sample code-

Mobile version

const scriptHash = 'cd948340ffcf11d4f5494140c93885583110f3e9';
const operation = 'test'
const args = [
    {
        type: 'String',
        value: 'helloworld'
    }
]
const gasPrice = 500;
const gasLimit = 20000;
const payer = 'AecaeSEBkt5GcBCxwz1F41TvdjX3dnKBkJ'
const config = {
    "login": true,
    "message": "invoke smart contract test",
    "qrcodeUrl": "" ,
    "callback": ""
}
const params = {
          scriptHash,
          operation,
          args,
          gasPrice,
          gasLimit,
          payer,
          config
        }
try {
   const res = await client.api.smartContract.invoke(params);
   } catch(err) {
    console.log(err)
}

Chrome version

const scriptHash = '16edbe366d1337eb510c2ff61099424c94aeef02';
const gasLimit = 30000;
const gasPrice = 500;
const operation = 'test'

const args = [
   {
    name: "msg",
    type: "String",
    value: "hello world"
   }
]
 params = {
            scriptHash,
            operation,
            args,
            gasPrice,
            gasLimit
}
await client.api.smartContract.invoke(params)

dAPI demonstration

The concepts explained above help create a foundation level understanding of how Ontology's dAPI works and a few ways in which it can used in a dApp.

The following demonstration will illustrate how the dAPI would function when integrated with a dApp, both the browser and mobile versions.

Here's a link to the sample mobile dApp http://101.132.193.149:5000/; the original code can be found here.

A browser based sample dApp is demonstrated below. The developers working with the Chrome plugin version may refer to the original code here.

First, the git repository needs to be cloned to the system and installed. The process can be carried out as follows.

$ git clone https://github.com/ontio-community/ontology-dapi-demo.git

$ npm install

$ npm run start

Message displayed in the shell command window

Upon successfully installing and running the application, it can be accessed using the address - http://localhost:3000.

Please ensure that the Cyano wallet Chrome extension is activated and running when the above page is opened.

Once the page opens, you can click on Provider, and then GetProvider on the next page to check whether or not the application is functioning properly. A prompt should display the version of Cyano you have installed.

At this point, the app has successfully established a connection and can interact with the chain by invoking the API. For instance, return to the main page and click on Network -> GetBlock. The app will return block related information, as such -

To demonstrate the functionality of the application we can carry out an account transfer. To do so, click on Asset -> Make Transfer. A default address will by default appear in the address field.

The transaction takes place on the test-net. Please ensure that your wallet is connected to the test net so as to carry out the authorization protocol and then later on see the changes reflect in your wallet.

The Cyano wallet's confirmation window will automatically pop up. Confirm the transaction, and then once the transaction completes, it can be confirmed using Ontology's Explorer by using your public address or the transaction hash the Chrome prompt will display.

At this point, the changes will be reflected in your wallet. The amount that you selected, along with 0.01 ONG (gas price) will be deducted from your wallet. Other transaction related details can be found in the explorer. The explorer can be accessed from here.