swift 如何删除可选字符串字符

如何删除可选字符

let color = colorChoiceSegmentedControl.titleForSegmentAtIndex(colorChoiceSegmentedControl.selectedSegmentIndex)

println(color) // Optional("Red")

let imageURLString = "http://hahaha.com/ha.php?color=\(color)"
println(imageURLString)
//http://hahaha.com/ha.php?color=Optional("Red")

我只是想要输出”http://hahaha.com/ha.php?color=红色"

我能怎么做？

hmm....

实际上，当您将任何变量定义为可选变量时，您需要解开该可选值。要解决此问题，您必须将变量声明为非选项，或者在变量后面放置 !（感叹号）标记以解开选项值。

var optionalVariable : String? // This is an optional.
optionalVariable = "I am a programer"
print(optionalVariable) // Optional("I am a programer")
        
var nonOptionalVariable : String // This is not optional.
nonOptionalVariable = "I am a programer"
print(nonOptionalVariable) // "I am a programer"

//There are different ways to unwrap optional varialble

// 1 (Using if let or if var)
if let optionalVariable1 = optionalVariable {
    print(optionalVariable1)
}

// 2 (Using guard let or guard var)
guard let optionalVariable2 = optionalVariable else {
    fatalError()
}
print(optionalVariable2)

// 3 (Using default value ?? )
print(optionalVariable ?? "default value") // If variable is empty it will return default value

// 4 (Using force caste !)
print(optionalVariable!) // This is unsafe way and may lead to crash