类型的值…没有成员

Question

I'm new to Swift and I'm learning it on iTunes U, using a Stanford University course. I'm programming a calculator. The instructor in the course video has the same code, software and same version of Xcode.

So here's the code for my ViewController :

@IBAction private func performOperation(sender: UIButton) {
    if userIsInTheMiddleOfTyping {
        brain.setOperand(displayValue)
        userIsInTheMiddleOfTyping = false
    }

    if let mathematicalSymbol = sender.currentTitle {
        brain.performOperation(mathematicalSymbol)
    }

    displayValue = brain.result
}

The error is in the last sentence: displayValue = brain.result :

Value of type 'CalculatorBrain' has no value 'result'

This a part of the CalculatorBrain code:

struct PendingBinaryOperationInfo {
    var BinaryFunction: (Double, Double) -> Double
    var firstOperand: Double }

    var result: Double { get { return 0.0 } }
}

So what's the problem?

PS All of the calculator functions aren't set to work yet. And the ode that some suggested,

 displayValue.text = "\(brain.result)"

didn't work at all and it gave me a ton of other errors.

Answer 1

Here you have a variable result declared as a property of a struct PendingBinaryOperationInfo . The variable result is not a property (at least not shown here) of a type CalculatorBrain wherever that may be. Hence the error.

You have:

struct PendingBinaryOperationInfo {
    var result: Double
}

When it's looking for:

class CalculatorBrain { // 'class' is just an example
    var result: Double
}

Answer 2

brain class don't have result this member, You need to check brain class is that a have result variable. The result may be private or internal variable so you can not use. It need to change to public member.