How can I inject and use this javascript library (web3) with JavascriptCore

Question

I have been trying to use the web3 library with JavascriptCore in Swift. A web3 instance is created by running

var web3 = new Web3(new Web3.providers.HttpProvider("[the provider im using]"))

This is the code I am trying to do this in Swift with:

if let url = Bundle.main.url(forResource: "web3", withExtension: "js"){
     let lib = try! String(contentsOfFile: url.path)
     let jsvirtualmachine = JSVirtualMachine()
     let context = JSContext(virtualMachine: jsvirtualmachine)
     context.evaluateScript(lib)

     let web3 = context.evaluateScript("var web3 = new Web3(new Web3.providers.HttpProvider('[myprovider]')")
     let fn = context.objectForKeyedSubscript("web3")
     let fn1 = fn?.construct(withArguments: [])
     let latestBlockNumber = context.evaluateScript("web3.eth.blockNumber")
     print(latestBlockNumber)
}

I have tried printing out latestBlockNumber, web3, fn, and fn1 and all of them return undefined

Any ideas?

Did you success with this try?

Aerok
– Aerok

2021-10-29 06:03:59 +00:00
Commented Oct 29, 2021 at 6:03 — Aerok
– Aerok, Commented Oct 29, 2021 at 6:03

stakri · Accepted Answer · 2017-11-01 21:51:09Z

4

The web3.js library has dependencies on bignumber.js and crypto-js.js (See dependencies here). You will need to add these two JS libs to the bundle and load them in a similar way, e.g.

do {
    let bigNumberJS = try String(contentsOf: Bundle.main.url(forResource: "bignumber.min", withExtension: "js")!, encoding: .utf8)
    let cryptoJS = try String(contentsOf: Bundle.main.url(forResource: "crypto-js", withExtension: "js")!, encoding: .utf8)
    let web3JS = try String(contentsOf: Bundle.main.url(forResource: "web3-light.min", withExtension: "js")!, encoding: .utf8)
    context.evaluateScript(bigNumberJS)
    context.evaluateScript(cryptoJS)
    context.evaluateScript(web3JS)
    context.evaluateScript("var Web3 = require('web3'); var web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'));")
    if let version = context.evaluateScript("web3.version.api") {
        print("Web3 version is \(version)")
    }
}
catch {
    print("An error occurred")
}

answered Nov 1, 2017 at 21:51

stakri

1,4171 gold badge12 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Aoke Li Over a year ago

hi, so unlike bignumber, crypto-js has multiple files. How to handle that?

stakri Over a year ago

Each of their releases contains a crypto-js.js which contains everything in one file. Try downloading the zip file of the latest release. github.com/brix/crypto-js/releases/tag/3.1.9-1

Collectives™ on Stack Overflow

How can I inject and use this javascript library (web3) with JavascriptCore

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related