Include Dictionary or Array Value in Swift String with Backslash Notation

include dictionary or array value in swift string with backslash notation

Single quotes are not allowed as string delimiters in Swift. Additionally the string interpolation does not allow ‘unescaped double quote (") or backslash (\)’, cf. The Swift Programming Language

If you have the key as a constant (or variable) it will work:

let key = "mine"
let str = "dictionary values are \(dict[key])"

As an aside Swift encourages immutability for safety, you should always use let by default and only revert to var if you really need to.

Swift : How to put string in \( )?

You can't put things with quotes in a \( ), you'll need to assign it to a variable:

var dictionary = ["name": "henry", "age": "20"];
let name = dictionary["name"];
println("name = \(name)");

escape dictionary key double quotes when doing println dictionary item in Swift

Xcode 7.1+

Since Xcode 7.1 beta 2, we can now use quotations within string literals. From the release notes:

Expressions interpolated in strings may now contain string literals. For example, "My name is (attributes["name"]!)" is now a valid expression. (14050788)

Xcode <7.1

I don't think you can do it that way.

From the docs

The expressions you write inside parentheses within an interpolated string cannot contain an unescaped double quote (") or backslash (\), and cannot contain a carriage return or line feed.

You'd have to use

let someVar = dict["key"]
println("Some words \(someVar)")

Swift string literal - remove escaping back slashes

You may be confusing how the IDE displays strings and the actual strings that would be printed. Setting breakpoints and looking at the debugger will show you C-escaped strings. If you print those values, the escaping will be gone. For example, if I create the literal string you're describing:

let string = #"[{"crawlLogic":{"startURL":"https://somesite.com/start","someParam":"\r\n\r\n/** Retrieves element's text either by class name""#

The debugger will print this value's debugDescription which will include escaping (such as \" and \\r, note the double-backslash):

print(string.debugDescription)
"[{\"crawlLogic\":{\"startURL\":\"https://somesite.com/start\",\"someParam\":\"\\r\\n\\r\\n/** Retrieves element\'s text either by class name\""

But those extra escapes aren't actually in the string:

print(string)
[{"crawlLogic":{"startURL":"https://somesite.com/start","someParam":"\r\n\r\n/** Retrieves element's text either by class name"

If the debugDescription has \r rather than \\r, then that's indicating you have a carriage return (UTF-8: 0x0d) in your string, not \r (UTF-8: 0x5c 0x72). If you need to convert carriage return + newline into \r\n, then you can do that with with replaceOccurrences(of:with:).

string.replaceOccurrences(of: "\r\n", with: #"\r\n"#)

This says to replace the string "carriage return, newline" with "backslash r backslash n."

(But I would first investigate why the string is in the wrong form to start with. I'm guessing you're constructing it with "\r\n" at some point when you meant #"\r\n"# or "\\r\\n". Or perhaps you're unescaping a string you were given when you shouldn't. Escaping and unescaping strings is very tricky. Try to build the string to hold the characters you want in the first place rather than trying to fix it later.)

If you continue to have trouble, I recommend converting your string into UTF-8 (Array(string.utf8)) and looking at the actual bytes. This will remove all ambiguity about what is in the string.

How to print double quotes inside ?

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)"#

Filtering dictionaries within array with JSON decoding based on latest date in Swift

I’d suggest to filter and then sort the array descending by the end date so the first item in the result is the latest entry. As first is an optional unwrap it safely

if let latestEntry = data.filter{$0.eventType == 201}
                         .sorted{$0.endDateTime > $1.endDateTime}
                         .first { …

Swift 5 : Convert Array/Dictionary to JSON format

You can create a model and encode to it like;

let yourArray = [
  (ingredient_item: "Oil", ingredient_item_id: "1", ingredient_qty: "1", ingredient_unit_id: "Tsp", ingredient_remark: ""),
  (ingredient_item: "Saffron", ingredient_item_id: "2", ingredient_qty: "2", ingredient_unit_id: "Tsp", ingredient_remark: ""),
  (ingredient_item: "Rice", ingredient_item_id: "3", ingredient_qty: "2", ingredient_unit_id: "Cup", ingredient_remark: "")
]

struct Model: Encodable {
    var ingredient_item: String
    var ingredient_item_id: String
    var ingredient_qty: String
    var ingredient_unit_id: String
    var ingredient_remark: String
}

let arr = yourArray.map({ Model(ingredient_item: $0,
                          ingredient_item_id: $1,
                          ingredient_qty: $2,
                          ingredient_unit_id: $3,
                          ingredient_remark: $4)})

let jsonData = try! JSONEncoder().encode(arr)
let jsonString = String(data: jsonData, encoding: .utf8)

What does backslash do in Swift?

The backslash has a few different meanings in Swift, depending on the context. In your case, it means string interpolation:

print("The total cost of my meal is \(dictionary["pizza"]! + dictionary["ice cream"]!)")

...is the same as:

print("The total cost of my meal is " + String(dictionary["pizza"]! + dictionary["ice cream"]!))

But the first form is more readable. Another example:

print("Hello \(person.firstName). You are \(person.age) years old")

Which may print something like Hello John. You are 42 years old. Much clearer than:

print("Hello " + person.firstName + ". You are " + String(person.age) + " years old")

Converting URL to String and back again

fileURLWithPath() is used to convert a plain file path (e.g. "/path/to/file") to an URL. Your urlString is a full URL string including the scheme, so you should use

let url = NSURL(string: urlstring)

to convert it back to NSURL. Example:

let urlstring = "file:///Users/Me/Desktop/Doc.txt"
let url = NSURL(string: urlstring)
println("the url = \(url!)")
// the url = file:///Users/Me/Desktop/Doc.txt

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