How to check object is nil or not in swift

Question

Suppose I have String like    var abc   NSString    ABC    and I want to check that it is nil or not and for that I try    if abc    nil             TODO           But this is not working and giving me an error  Error Says    Can not invoke     with an argument list of type     value NSString   NilLiteralConvertible      Any solution for this

User · Accepted Answer

If abc is an optional  then the usual way to do this would be to attempt to unwrap it in an if statement   if let variableName   abc      If casting  use  eg  if let var   abc as  NSString        variableName will be abc  unwrapped   else          abc is nil       However  to answer your actual question  your problem is that you re typing the variable such that it can never be optional   Remember that in Swift  nil is a value which can only apply to optionals   Since you ve declared your variable as   var abc  NSString       it is not optional  and cannot be nil   Try declaring it as   var abc  NSString        or alternatively letting the compiler infer the type

User · Answer

Swift short expression   var abc    string  abc    nil   doWork abc         or   abc    nil        abc    string    or both   abc    nil   doWork abc    abc    string

User · Answer

func isObjectValid someObject  Any   - gt  Any        if someObject is String           if let someObject   someObject as  String               return someObject          else               return                   else if someObject is Array lt Any gt            if let someObject   someObject as  Array lt Any gt                return someObject          else               return                   else if someObject is Dictionary lt AnyHashable  Any gt            if let someObject   someObject as  Dictionary lt String  Any gt                return someObject          else               return                    else if someObject is Data           if let someObject   someObject as  Data               return someObject          else               return Data                  else if someObject is NSNumber           if let someObject   someObject as  NSNumber              return someObject          else               return NSNumber init booleanLiteral  false                 else if someObject is UIImage           if let someObject   someObject as  UIImage               return someObject          else               return UIImage                       else           return  InValid Object            This function checks any kind of object and return s default value of the kind of object  if object is invalid

User · Answer

The null check is really done nice with guard keyword in swift  It improves the code readability and the scope of the variables are still available after the nil checks if you want to use them   func setXYX - gt  Void        guard a    nil  else           return             guard  b    nil else           return             print    a and b is not null

User · Answer

Normally  I just want to know if the object is nil or not   So i use this function that just returns true when the object entered is valid and false when its not   func isNotNil someObject  Any   - gt  Bool           if someObject is String               if  someObject as  String     nil                   return true              else                   return false                        else if someObject is Array lt Any gt                if  someObject as  Array lt Any gt      nil                   return true              else                   return false                        else if someObject is Dictionary lt AnyHashable  Any gt                if  someObject as  Dictionary lt String  Any gt      nil                   return true              else                   return false                        else if someObject is Data               if  someObject as  Data     nil                   return true              else                   return false                        else if someObject is NSNumber               if  someObject as  NSNumber     nil                  return true              else                   return false                        else if someObject is UIImage               if  someObject as  UIImage     nil                   return true              else                   return false                                 return false

User · Answer

Swift-5 Very Simple Way     MARK - In my case i have an array so i am checking the object in this     for object in yourArray           if object is NSNull               print  Hey  it s null              else if object is String               print  Hey  it s String              else if object is Int               print  Hey  it s Int              else if object is yourChoice               print  Hey  it s yourChoice                       else               print  It s not null  not String  not yourChoice it s   object

User · Answer

I ended up writing utility function for nil check  func isObjectNotNil object AnyObject   - gt  Bool       if let   AnyObject   object               return true            return false     Does the same job  amp  code looks clean   Usage  var someVar NSNumber    if isObjectNotNil someVar       print  Object is NOT nil     else      print  Object is nil

User · Answer

The case of if abc    nil is used when you are declaring a var and want to force unwrap and then check for null  Here you know this can be nil and you can check if    nil use the NSString functions from foundation    In case of String  you are not aware what is wrapped at runtime and hence you have to use if-let and perform the check   You were doing following but without      Hope this clears it   From apple docs look at this   let assumedString  String     An implicitly unwrapped optional string     You can still treat an implicitly unwrapped optional like a normal optional  to check if it contains a value   if assumedString    nil       println assumedString       prints  An implicitly unwrapped optional string

User · Answer

Swift 4 You cannot compare Any to nil Because an optional can be nil and hence it always succeeds to true  The only way is to cast it to your desired object and compare it to nil   if  someone as  String     nil        your code enter code here

User · Answer

Swift 4 2  func isValid   object AnyObject   - gt  Bool       if let   AnyObject   object               return true            return false     Usage    if isValid selectedPost        savePost

User · Answer

if  MyUnknownClassOrType is nil        println  No class or object to see here       Apple also recommends that you use this to check for depreciated and removed classes from previous frameworks   Here s an exact quote from a developer at Apple      Yes  If the currently running OS doesn   t implement the class then the class method will return nil    Hope this helps

[swift] How to check object is nil or not in swift?

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