Swift 二进制运算符'<'；无法应用于类型为'；双倍'；和'；CGFloat&x27；

此代码没有语法错误

for (var m = 1.0; m < 3.0; m += 0.1) {
}

for（var m=1.0；m<3.0；m+=0.1）{
}

另一方面，下面的代码有语法错误。

---

错误消息：二进制运算符'，因为

image！。size.height

return

CGFloat

任何类型的

n

都是

Double

，因此您需要将

CGFloat

转换为

Double

这样

Double（image！.size.height）

您的代码将是：

let image = UIImage(named: "myImage")

for (var n = 1.0; n < Double(image!.size.height); n += 0.1) {

}

---

实现这一点的一种稍微经典的方法是使用

stride（）

函数系列

// Create the image, crashing if it doesn't exist. since the error case has been handled, there is no need to force unwrap the image anymore.
guard let image = UIImage(named: "myImage") else { fatalError() }

// The height parameter returns a CGFloat, convert it to a Double for consistency across platforms.
let imageHeight = Double(image.size.height)

// Double conforms to the `Strideable` protocol, so we can use the stride(to:by:) function to enumerate through a range with a defined step value.
for n in 1.0.stride(to: imageHeight, by: 0.1) {
    print("\(n)")
    // ... Or do whatever you want to in here.
}

---

请在Swift 4.0上查看此项

var enteringAmountDouble: Double? {
    return Double(amountTextField.text!)
}
var userMoneyDouble: Double? = userWalletMerchants?.balance
if (enteringAmountDouble?.isLessThanOrEqualTo(userMoneyDouble!))! {
    print("Balance is there .. U can transfer money to someone!")
}else{
    APIInterface.instance().showAlert(title: "Please check you are balance", message: "Insufficient balance")
    return
}

---

您是否检查了

的操作数类型谢谢您的建议。我没有得到证实。下次我会检查类型。哦，我误解了“1.0”是作为CGFloat构建的。我也误解了错误信息所说的。非常感谢你的回答。我没有确认。哇！这是最好的方式！！我不知道Streable协议，但主要类型，比如Double、Float、Int，符合这个。这很明显，我很兴奋！！谢谢你的建议！我用这个！
// Create the image, crashing if it doesn't exist. since the error case has been handled, there is no need to force unwrap the image anymore.
guard let image = UIImage(named: "myImage") else { fatalError() }

// The height parameter returns a CGFloat, convert it to a Double for consistency across platforms.
let imageHeight = Double(image.size.height)

// Double conforms to the `Strideable` protocol, so we can use the stride(to:by:) function to enumerate through a range with a defined step value.
for n in 1.0.stride(to: imageHeight, by: 0.1) {
    print("\(n)")
    // ... Or do whatever you want to in here.
}

var enteringAmountDouble: Double? {
    return Double(amountTextField.text!)
}
var userMoneyDouble: Double? = userWalletMerchants?.balance
if (enteringAmountDouble?.isLessThanOrEqualTo(userMoneyDouble!))! {
    print("Balance is there .. U can transfer money to someone!")
}else{
    APIInterface.instance().showAlert(title: "Please check you are balance", message: "Insufficient balance")
    return
}