你可以通过以下方式添加字符串:

str += “” str = str + “” str = str + str2 str = “” + “” str = “\（变量）” str = str + “\（变量）”

我想我把它们都叫出来了。

在Swift 5中，apple引入了使用#符号的原始字符串。

例子:

print(#"My name is "XXX" and I'm "28"."#)
let name = "XXX"
print(#"My name is \#(name)."#)

符号#必须在\后面。常规的\(name)将被解释为字符串中的字符。

斯威夫特4.2

你也可以使用扩展:

extension Array where Element == String? {
    func compactConcate(separator: String) -> String {
        return self.compactMap {
            if let unwrappedString = $0,
               unwrappedString.isEmpty {
                return nil
            } else {
                return $0
            }
        }
        .joined(separator: separator)
    }
}

Use:

label.text = [m.firstName, m.lastName].compactConcate(separator: " ")

结果:

"The Man"
"The"
"Man"

快速连接字符串

关于性能的几句话

UI测试包在iPhone 7(真实设备)，iOS 14， -Onone(调试，没有优化)[关于]

var result = ""
for i in 0...count {
    <concat_operation>
}

计数= 5_000

//Append
result.append(String(i))                         //0.007s 39.322kB

//Plus Equal
result += String(i)                              //0.006s 19.661kB

//Plus
result = result + String(i)                      //0.130s 36.045kB

//Interpolation
result = "\(result)\(i)"                         //0.164s 16.384kB

//NSString
result = NSString(format: "%@%i", result, i)     //0.354s 108.142kB

//NSMutableString
result.append(String(i))                         //0.008s 19.661kB

禁用下一个测试:

加上高达100_000 ~10s 插补可达100_000 ~10s NSString高达10_000 ->内存问题

Count = 1_000_000

//Append
result.append(String(i))                         //0.566s 5894.979kB

//Plus Equal
result += String(i)                              //0.570s 5894.979kB

//NSMutableString
result.append(String(i))                         //0.751s 5891.694kB

*注意将Int转换为字符串

源代码

import XCTest

class StringTests: XCTestCase {
    let count = 1_000_000
    
    let metrics: [XCTMetric] = [
        XCTClockMetric(),
        XCTMemoryMetric()
    ]
    
    let measureOptions = XCTMeasureOptions.default
    
    override func setUp() {
        measureOptions.iterationCount = 5
    }
    
    func testAppend() {
        var result = ""
        measure(metrics: metrics, options: measureOptions) {
            for i in 0...count {
                result.append(String(i))
            }
        }
    }
    
    func testPlusEqual() {
        var result = ""
        measure(metrics: metrics, options: measureOptions) {
            for i in 0...count {
                result += String(i)
            }
        }
    }
    
    func testPlus() {
        var result = ""
        measure(metrics: metrics, options: measureOptions) {
            for i in 0...count {
                result = result + String(i)
            }
        }
    }
    
    func testInterpolation() {
        var result = ""
        measure(metrics: metrics, options: measureOptions) {
            for i in 0...count {
                result = "\(result)\(i)"
            }
        }
    }
    
    //Up to 10_000
    func testNSString() {
        var result: NSString =  ""
        measure(metrics: metrics, options: measureOptions) {
            for i in 0...count {
                result = NSString(format: "%@%i", result, i)
            }
        }
    }
    
    func testNSMutableString() {
        let result = NSMutableString()
        measure(metrics: metrics, options: measureOptions) {
            for i in 0...count {
                result.append(String(i))
            }
        }
    }
}

斯威夫特5:

数组的字符串变成一个单一的字符串

let array = ["Ramana","Meharshi","Awareness","Oneness","Enlightnment","Nothing"]
let joined = array.joined(separator: ",")

非常简单:

let StringA = "Hello"
let StringB = "World"
let ResultString = "\(StringA)\(StringB)"
println("Concatenated result = \(ResultString)")