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
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-
Mobile version-
2. Initialization
A contract must be initialized before it is invoked.
Chrome version
Mobile version
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 orONT ID
. If the information can be retrieved successfully, it indicates the logged in state with respect to thedApp
.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 thedApp
.
For more information on the method to implement back end signature verification, consider referring-
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
Chrome version
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
Chrome version
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
Chrome version
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.
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.
Last updated