无法使用“（_）”类型的参数列表调用“执行”

Question

为什么这个 Square 示例直接因为他们的 README 不起作用？

    let callbackURL = URL(string: "OdinMobile://")!
    do {
        let amount = try SCCMoney(amountCents: money, currencyCode: "USD")

        let request : SCCAPIRequest =
            try SCCAPIRequest(
                callbackURL: callbackURL,
                amount: amount,
                userInfoString: userInfoString,
                merchantID: nil,
                notes: notes,
                customerID: nil,
                supportedTenderTypes: supportedTenderTypes,
                clearsDefaultFees: clearsDefaultFees,
                returnAutomaticallyAfterPayment: true
            )

    } catch let error as NSError {
        print(error.localizedDescription)
    }

    do {
        try SCCAPIConnection.perform(request)
    } catch let error as NSError {
        print(error.localizedDescription)
    }

我收到了一个 Cannot invoke 'perform' with an argument list of type '(_)' 和一条附加消息 Overloads for 'perform' exist with these partially matching parameter lists: (SCCAPIRequest), (Selector!)。我希望request 成为一个 SCCAPIRequest，为什么它不作为一个读取？是因为它在do 块中吗？

Answer 1

do 关键字在其花括号内创建了一个范围，例如 if 或 for 循环，这意味着您创建的请求在第一个范围内，而在第二个范围内不可用。由于在这两种情况下，您都在做同样的事情并出现相同的错误，因此您只需将 perform 调用移动到同一范围内即可。

let callbackURL = URL(string: "OdinMobile://")!
do {
    let amount = try SCCMoney(amountCents: money, currencyCode: "USD")

    let request : SCCAPIRequest =
        try SCCAPIRequest(
            callbackURL: callbackURL,
            amount: amount,
            userInfoString: userInfoString,
            merchantID: nil,
            notes: notes,
            customerID: nil,
            supportedTenderTypes: supportedTenderTypes,
            clearsDefaultFees: clearsDefaultFees,
            returnAutomaticallyAfterPayment: true
        )
    try SCCAPIConnection.perform(request)
} catch let error as NSError {
    print(error.localizedDescription)
}