Swift: Cannot convert return expression of type 'Promise<Int>' to return type 'Int'

Question

I try to return data from an ERC20 Token in Ganache and show it in my SwiftUI View(). To do so I wanted to use PromiseKit. The following code describes what I want to do:

func getTotalSupply(contractAddress: String) -> Int {
        let address = try! EthereumAddress(hex: contractAddress, eip55: true)
        let contract = web3.eth.Contract(type: erc20Token.self, address: address)
        
        return firstly {
            try! contract.totalSupply().call()
        }.map { supply -> Int in
            let value = supply["_totalSupply"] as! Int
            return value
        }
    }

I receive the following error at the .map operation:

Cannot convert return expression of type 'Promise<Int>' to return type 'Int'

I could return Promise<Int> from the function, but I can't display a Promise in my View(). How do I turn a Promise<Int> into an Int? I tried to google this for several hours, but I am still clueless.

Answer 1

等待大神答复