无法将类型'NSArray'的值分配给类型'[AnyObject]'的值

Question

In swift, I have an School class, it has an students property of type [AnyObject]!

class School : NSObject {
  var students: [AnyObject]!
  ...
}

I got an instance of School , and an NSArray of string representing students' names. I want to assign this NSArray variable to students :

var school = School()
var studentArray : NSArray = getAllStudents()

//ERROR:Cannot assign a value of type 'NSArray' to a value of type '[AnyObject]'
school.students = studentArray

Why this error? Isn't array in swift compatible with NSArray in objective c??? How to get rid of above compiler error?

Answer 1

Your var students is a Swift array and expects object of type AnyObject , but you try assign it an NSArray . The two objects are not of the same type and it doesn't work.

But, given that NSArray is compatible with [AnyObject] , you can use simple typecasting to make the NSArray into a Swift array:

school.students = studentArray as [AnyObject]

Of course a better approach would be to stay in the Swift world and to forget NSArray altogether if possible, by making getAllStudents return a Swift array instead of an NSArray. Not only you will avoid having to do typecasts but you will also benefit from the power of the Swift collections.

Answer 2

Sounds like school.students is defined as Optional and might be nil therefore if you are sure that its not nil - unwrap it first by using !:

school.students as AnyObject! as NSArray

OR

school.students! as NSArray

Answer 3

My method written in object c which return NSMutableArray of type "Database"

 -(NSMutableArray *)AllRowFromTableName:(NSString *)tableName;

In swift i declare variable as

var petListArray: NSMutableArray = []

Save in model array as

 self.petListArray = self.dataBase.AllRowFromTableName("InsuranceTable")

Used in cellForRowAtIndexPath

 let tempDBObject = self.petListArray[indexPath.row] as! Database
 cell?.petName.text = tempDBObject.Hname

hope this help someone.