我怎样才能迅速地画出一条新的线呢

You should be able to use \n inside a Swift string, and it should work as expected, creating a newline character. You will want to remove the space after the \n for proper formatting like so:

var example: String = "Hello World \nThis is a new line"

Which, if printed to the console, should become:

Hello World
This is a new line

However, there are some other considerations to make depending on how you will be using this string, such as:

• If you are setting it to a UILabel's text property, make sure that the UILabel's numberOfLines = 0, which allows for infinite lines.
• In some networking use cases, use \r\n instead, which is the Windows newline.

Edit: You said you're using a UITextField, but it does not support multiple lines. You must use a UITextView.

You can use the following code;

var example: String = "Hello World \r\n This is a new line"

Also useful:

let multiLineString = """
Line One
Line Two
Line Three
"""

• Makes the code read more understandable
• Allows copy pasting

You can do this

textView.text = "Name: \(string1) \n" + "Phone Number: \(string2)"

The output will be

Name: output of string1 Phone Number: output of string2

"\n" is not working everywhere!

For example in email, it adds the exact "\n" into the text instead of a new line if you use it in the custom keyboard like: textDocumentProxy.insertText("\n")

There are another newLine characters available but I can't just simply paste them here (Because they make a new lines).

using this extension:

extension CharacterSet {
var allCharacters: [Character] {
var result: [Character] = []
for plane: UInt8 in 0...16 where self.hasMember(inPlane: plane) {
for unicode in UInt32(plane) << 16 ..< UInt32(plane + 1) << 16 {
if let uniChar = UnicodeScalar(unicode), self.contains(uniChar) {
result.append(Character(uniChar))
}
}
}
return result
}
}

you can access all characters in any CharacterSet. There is a character set called newlines. Use one of them to fulfill your requirements:

let newlines = CharacterSet.newlines.allCharacters
for newLine in newlines {
print("Hello World \(newLine) This is a new line")
}

Then store the one you tested and worked everywhere and use it anywhere. Note that you can't relay on the index of the character set. It may change.

But most of the times "\n" just works as expected.