在swift 2.0中,print()
会自动添加换行符。在swift 1.2中,println()
和print()
曾经是单独的函数。因此,如何打印一些文本而不添加换行符,因为swift不再具有不附加换行符的打印功能。
答案 0 :(得分:167)
从Swift 2.0开始,推荐的不带换行符的打印方法是:
print("Hello", terminator:"")
答案 1 :(得分:62)
print
函数自 Swift 的后期修订版以来已完全改变,现在看起来更简单,并且有方法的变体可以打印到标准控制台。
print的方法签名看起来像这样,
public func print<Target>(_ items: Any..., separator: String = default, terminator: String = default, to output: inout Target) where Target : TextOutputStream
以下是一些用例,
print("Swift is awesome.")
print("Swift", "is", "awesome", separator:" ")
print("Swift", "is", "awesome", separator:" ", terminator:".")
打印:
Swift is awesome.
Swift is awesome
Swift is awesome.
<强>级联强>
print("This is wild", terminator: " ")
print("world")
打印:
This is wild world
因此,使用终结符时,应注意内容与同一行相关。
使用 CustomStringConvertible打印对象
struct Address {
let city: String
}
class Person {
let name = "Jack"
let addresses = [
Address(city: "Helsinki"),
Address(city: "Tampere")
]
}
extension Person: CustomStringConvertible {
var description: String {
let objectAddress = unsafeBitCast(self, to: Int.self)
return String(format: "<name: \(name) %p>", objectAddress)
}
}
let jack = Person()
print(jack)
打印:
<name: Jack 0x608000041c20>
<强> CustomDebugStringConvertible 强>
extension Person: CustomDebugStringConvertible {
var debugDescription: String {
let objectAddress = unsafeBitCast(self, to: Int.self)
let addressString = addresses.map { $0.city }.joined(separator: ",")
return String(format: "<name: \(name), addresses: \(addressString) %p>",objectAddress)
}
}
现在,使用 lldb ,您可以使用 po 命令,它将在lldb控制台中打印对象,
<name: Jack, addresses: Helsinki,Tampere 0x60c000044860>
使用 TextOutputStream
记录到文件struct MyStreamer: TextOutputStream {
lazy var fileHandle: FileHandle? = {
let fileHandle = FileHandle(forWritingAtPath: self.logPath)
return fileHandle
}()
var logPath: String = "My file path"
mutating func write(_ string: String) {
fileHandle?.seekToEndOfFile()
fileHandle?.write(string.data(using:.utf8)!)
}
}
现在,使用print来流式传输,
print("First of all", to: &myStream )
print("Then after", to: &myStream)
print("And, finally", to: &myStream)
打印到文件:
First of all
Then after
And finally
<强> CustomReflectable 强>
extension Person: CustomReflectable {
var customMirror: Mirror {
return Mirror(self, children: ["name": name, "address1": addresses[0], "address2": addresses[1]])
}
}
现在,在lldb调试器中,如果使用命令po,
> po person
结果将是这样的,
▿ <name: Jack, addresses: Tampere Helsinki 0x7feb82f26e80>
- name : "Jack"
▿ address1 : Address
- city : "Helsinki"
▿ address2 : Address
- city : "Tampere"
答案 2 :(得分:9)
在Swift 2.0中,你可以这样做:
基本版
print("Hello World")
result "Hello World\n"
使用终结者
print("Hello World", terminator:"")
result "Hello World"
使用分隔符
print("Hello", "World", separator:" ")
result "Hello World\n"
使用分隔符和终结符
print("Hello", "World", separator:" ", terminator:"")
result "Hello World"
使用一个变量
var helloworld = "Hello World"
print(helloworld)
result "Hello World\n"
使用两个变量
var hello = "Hello"
var world = "World"
print (hello, world)
result "Hello World\n"
答案 3 :(得分:4)
如果你想在循环中使用相同的行:
for i in 1...4
{
print("", i, separator: " ", terminator:"")
}
print()
输出:1 2 3 4