How to print double quotes inside ""?

Question

With a backslash before the double quote you want to insert in the String:

let sentence = "They said \"It's okay\", didn't they?"

Now sentence is:

They said "It's okay", didn't they?

It's called "escaping" a character: you're using its literal value, it will not be interpreted.

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With Swift 4 you can alternatively choose to use the """ delimiter for literal text where there's no need to escape:

let sentence = """
They said "It's okay", didn't they?
Yes, "okay" is what they said.
"""

This gives:

They said "It's okay", didn't they?
Yes, "okay" is what they said.

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With Swift 5 you can use enhanced delimiters:

String literals can now be expressed using enhanced delimiters. A string literal with one or more number signs (#) before the opening quote treats backslashes and double-quote characters as literal unless they’re followed by the same number of number signs. Use enhanced delimiters to avoid cluttering string literals that contain many double-quote or backslash characters with extra escapes.

Your string now can be represented as:

let sentence = #"They said "It's okay", didn't they?"#

And if you want add variable to your string you should also add # after backslash:

let sentence = #"My "homepage" is \#(url)"#

For completeness, from Apple docs:

String literals can include the following special characters:

• The escaped special characters \0 (null character), \ (backslash), \t (horizontal tab), \n (line feed), \r (carriage return), \" (double quote) and \' (single quote)
• An arbitrary Unicode scalar, written as \u{n}, where n is a 1–8 digit hexadecimal number with a value equal to a valid Unicode code point

which means that apart from being able to escape the character with backslash, you can use the unicode value. Following two statements are equivalent:

let myString = "I love \"unnecessary\" quotation marks"
let myString = "I love \u{22}unnecessary\u{22} quotation marks"

myString would now contain:

I love "unnecessary" quotation marks

According to your needs, you may use one of the 4 following patterns in order to print a Swift String that contains double quotes in it.

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1. Using escaped double quotation marks

String literals can include special characters such as \":

let string = "A string with \"double quotes\" in it."
print(string) //prints: A string with "double quotes" in it.

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2. Using Unicode scalars

String literals can include Unicode scalar value written as \u{n}:

let string = "A string with \u{22}double quotes\u{22} in it."
print(string) //prints: A string with "double quotes" in it.

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3. Using multiline string literals (requires Swift 4)

The The Swift Programming Language / Strings and Characters states:

Because multiline string literals use three double quotation marks instead of just one, you can include a double quotation mark (") inside of a multiline string literal without escaping it.

let string = """
A string with "double quotes" in it.
"""
print(string) //prints: A string with "double quotes" in it.

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4. Using raw string literals (requires Swift 5)

The The Swift Programming Language / Strings and Characters states:

You can place a string literal within extended delimiters to include special characters in a string without invoking their effect. You place your string within quotation marks (") and surround that with number signs (#). For example, printing the string literal #"Line 1\nLine 2"# prints the line feed escape sequence (\n) rather than printing the string across two lines.

let string = #"A string with "double quotes" in it."#
print(string) //prints: A string with "double quotes" in it.