Check string for nil empty

Question

Is there a way to check strings for nil and    in Swift  In Rails  I can use blank   to check    I currently have this  but it seems overkill       if stringA     nil           if  stringA  isEmpty                  blah blah

User · Answer

You should do something like this  if   string  isEmpty    true      Not nil nor empty    Nil coalescing operator checks if the optional is not nil  in case it is not nil it then checks its property  in this case isEmpty  Because this optional can be nil you provide a default value which will be used when your optional is nil

User · Answer

You could perhaps use the if-let-where clause   Swift 3   if let string   string   string isEmpty          string is not blank        Swift 2   if let string   string where  string isEmpty          string is not blank

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Create a String class extension   extension String         returns false if passed string is nil or empty     static func isNilOrEmpty   string String   - gt  Bool         if  string    nil                     return true           return string  isEmpty           extension  String   Notice this will return TRUE if the string contains one or more blanks  To treat blank string as  empty   use      return string  trimmingCharacters in  CharacterSet whitespaces  isEmpty       instead  This requires Foundation   Use it thus     if String isNilOrEmpty  hello world      true      print  it s a string

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With Swift 5  you can implement an Optional extension for String type with a boolean property that returns if an optional string is empty or has no value  extension Optional where Wrapped    String        var isEmptyOrNil  Bool           return self  isEmpty    true           However  String implements isEmpty property by conforming to protocol Collection  Therefore we can replace the previous code s generic constraint  Wrapped    String  with a broader one  Wrapped  Collection  so that Array  Dictionary and Set also benefit our new isEmptyOrNil property  extension Optional where Wrapped  Collection        var isEmptyOrNil  Bool           return self  isEmpty    true            Usage with Strings  let optionalString  String    nil print optionalString isEmptyOrNil     prints  true  let optionalString  String     quot  quot  print optionalString isEmptyOrNil     prints  true  let optionalString  String     quot Hello quot  print optionalString isEmptyOrNil     prints  false  Usage with Arrays  let optionalArray  Array lt Int gt     nil print optionalArray isEmptyOrNil     prints  true  let optionalArray  Array lt Int gt        print optionalArray isEmptyOrNil     prints  true  let optionalArray  Array lt Int gt      10  22  3  print optionalArray isEmptyOrNil     prints  false   Sources   swiftbysundell com - Extending optionals in Swift objc io - Swift Tip  Non-Empty Collections

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Swift 3 For check Empty String best way  if  string isEmpty      do stuff

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When dealing with passing values from local db to server and vice versa  I was having too much trouble with   s and   s and what not   So I made a Swift3 0 utility to handle null cases and i can almost totally avoid   s and   s in the code   func str   string  String   - gt  String       return  string    nil   string            Ex -  Before        let myDictionary   String  String                             title    dbObject  title    nil   dbObject  title           After        let myDictionary   String  String                               title   str dbObject title     and when its required to check for a valid string       if  str dbObject title  isEmpty             do stuff         This saved me having to go through the trouble of adding and removing numerous   s and   s after writing code that reasonably make sense

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In my opinion  the best way to check the nil and empty string is to take the string count   var nilString   String  print nilString count     count is nil  var emptyString      print emptyString count     count is 0     combine both conditions for optional string variable if string  count    nil    string  count    0      print  Your string is either empty or nil

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This is a general solution for all types that conform to the Collection protocol  which includes String  extension Optional where Wrapped  Collection       var isNilOrEmpty  Bool           self  isEmpty    true

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Using the guard statement I was using Swift for a while before I learned about the guard statement  Now I am a big fan  It is used similarly to the if statement  but it allows for early return and just makes for much cleaner code in general  To use guard when checking to make sure that a string is neither nil nor empty  you can do the following  let myOptionalString  String    nil  guard let myString   myOptionalString   myString isEmpty else       print  quot String is nil or empty  quot       return    or break  continue  throw        myString is neither nil nor empty  if this point is reached  print myString   This unwraps the optional string and checks that it isn t empty all at once  If it is nil  or empty   then you return from your function  or loop  immediately and everything after it is ignored  But if the guard statement passes  then you can safely use your unwrapped string  See Also  Statements documentation The Guard Statement in Swift 2

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SWIFT 3  extension Optional where Wrapped    String            Checks to see whether the optional string is nil or empty          public var isNilOrEmpty  Bool           if let text   self   text isEmpty   return false           return true           Use like this on optional string   if myString isNilOrEmpty   print  Crap  how d this happen

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Swift 3 This works well to check if the string is really empty  Because isEmpty returns true when there s a whitespace   extension String       func isEmptyAndContainsNoWhitespace   - gt  Bool           guard self isEmpty  self trimmingCharacters in   whitespaces  isEmpty             else                  return false                   return true           Examples   let myString    My String  myString isEmptyAndContainsNoWhitespace      returns false  let myString      myString isEmptyAndContainsNoWhitespace      returns true  let myString       myString isEmptyAndContainsNoWhitespace      returns false

User · Answer

If you re dealing with optional Strings  this works    string        isEmpty   The    nil coalescing operator returns the left side if it s non-nil  otherwise it returns the right side   You can also use it like this to return a default value    string        isEmpty    Default    string

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helpful when getting value from UITextField  and checking for nil  amp  empty string   IBOutlet weak var myTextField  UITextField    Heres your function  when you tap on a button  that gets string from UITextField and does some other stuff   IBAction func getStringFrom myTextField   sender  Any     guard let string   myTextField text    myTextField text  isEmpty    else   return         use  string  to do your stuff      This will take care of nil value as well as empty string   It worked perfectly well for me

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You can create your own custom function  if that is something you expect to do a lot   func isBlank  optionalString  String   - gt  Bool       if let string   optionalString           return string isEmpty       else           return true            var optionalString  String    nil  if isBlank optionalString        println  here     else       println  there

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var str  String    nil  if str  isEmpty    true       print  str is nil or empty      str       if str  isEmpty    true       print  str is nil or empty

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Swift 3 solution Use the optional unwrapped value and check against the boolean   if  string  isempty    true           Perform action

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Using isEmpty   Hello  isEmpty     false    isEmpty          true   Using allSatisfy  extension String     var isBlank  Bool       return allSatisfy    0 isWhitespace            Hello  isBlank           false    isBlank                true   Using optional String  extension Optional where Wrapped    String     var isBlank  Bool       return self  isBlank    true        var title  String    nil title isBlank               true title                     title isBlank               true   Reference   https   useyourloaf com blog empty-strings-in-swift

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I know there are a lot of answers to this question  but none of them seems to be as convenient as this  in my opinion  to validate UITextField data  which is one of the most common cases for using it   extension Optional where Wrapped    String       var isNilOrEmpty  Bool           return self  trimmingCharacters in   whitespaces  isEmpty    true           You can just use   textField text isNilOrEmpty   You can also skip the  trimmingCharacters in  whitespaces  if you don t consider whitespaces as an empty string or use it for more complex input tests like   var isValidInput  Bool       return  isNilOrEmpty  amp  amp  self  trimmingCharacters in   whitespaces  characters count  gt   MIN CHARS

User · Answer

If you want to access the string as a non-optional  you should use Ryan s Answer  but if you only care about the non-emptiness of the string  my preferred shorthand for this is  if stringA  isEmpty    false          blah blah     Since    works fine with optional booleans  I think this leaves the code readable without obscuring the original intention   If you want to check the opposite  if the string is nil or     I prefer to check both cases explicitly to show the correct intention   if stringA    nil    stringA  isEmpty    true          blah blah

User · Answer

I would recommend   if stringA map isEmpty     false       println  blah blah       map applies the function argument if the optional is  Some  The playground capture also shows another possibility with the new Swift 1 2 if let optional binding

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Use the ternary operator  also known as the conditional operator  C   forever     if stringA    nil   stringA  isEmpty    false   false                The stringA  force-unwrapping happens only when stringA    nil  so it is safe  The    false verbosity is somewhat more readable than yet another exclamation mark in   stringA  isEmpty    I personally prefer a slightly different form   if stringA    nil   false   stringA  isEmpty    false                In the statement above  it is immediately very clear that the entire if block does not execute when a variable is nil

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you can use this func      class func stringIsNilOrEmpty aString  String  - gt  Bool   return  aString  isEmpty

User · Answer

If you are using Swift 2  here is an example my colleague came up with  which adds isNilOrEmpty property on optional Strings   protocol OptionalString    extension String  OptionalString     extension Optional where Wrapped  OptionalString       var isNilOrEmpty  Bool           return   self as  String         isEmpty           You can then use isNilOrEmpty on the optional string itself  func testNilOrEmpty         let nilString String    nil     XCTAssertTrue nilString isNilOrEmpty       let emptyString String           XCTAssertTrue emptyString isNilOrEmpty       let someText String     lorem      XCTAssertFalse someText isNilOrEmpty

[swift] Check string for nil & empty

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