How to resize Title in a navigation bar dynamically

Used the below code in ViewDidload .

Objective C

self.title = @"Your TiTle Text";
UILabel* tlabel=[[UILabel alloc] initWithFrame:CGRectMake(0,0, 200, 40)];
tlabel.text=self.navigationItem.title;
tlabel.textColor=[UIColor whiteColor];
tlabel.font = [UIFont fontWithName:@"Helvetica-Bold" size: 30.0];
tlabel.backgroundColor =[UIColor clearColor];
tlabel.adjustsFontSizeToFitWidth=YES;
tlabel.textAlignment = NSTextAlignmentCenter;
self.navigationItem.titleView=tlabel;

Swift Version

self.title = "Your Title Text"
let tlabel = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 40))
tlabel.text = self.title
tlabel.textColor = UIColor.white
tlabel.font = UIFont.systemFont(ofSize: 30, weight: .bold)
tlabel.backgroundColor = UIColor.clear
tlabel.adjustsFontSizeToFitWidth = true
tlabel.textAlignment = .center
self.navigationItem.titleView = tlabel

Hope it works for you.Thanks

This works for me

Objective C

[UILabel appearanceWhenContainedInInstancesOfClasses:@[[UINavigationBar class]]].adjustsFontSizeToFitWidth = YES;

Swift Version

UILabel.appearance(whenContainedInInstancesOf: [UINavigationBar.self]).adjustsFontSizeToFitWidth = true

Swift version of Accepted Answer + putting the label text on center :

Swift 2.3:

    self.title = "Your TiTle Text"
    let tlabel = UILabel(frame: CGRectMake(0, 0, 200, 40))
    tlabel.text = self.title
    tlabel.textColor = UIColor.whiteColor()
    tlabel.font = UIFont.boldSystemFontOfSize(17) //UIFont(name: "Helvetica", size: 17.0)
    tlabel.backgroundColor = UIColor.clearColor()
    tlabel.adjustsFontSizeToFitWidth = true
    tlabel.textAlignment = .Center
    self.navigationItem.titleView = tlabel

And Swift 3 :

    self.title = "Your TiTle Text"
    let frame = CGRect(x: 0, y: 0, width: 200, height: 40)
    let tlabel = UILabel(frame: frame)
    tlabel.text = self.title
    tlabel.textColor = UIColor.white
    tlabel.font = UIFont.boldSystemFont(ofSize: 17) //UIFont(name: "Helvetica", size: 17.0)
    tlabel.backgroundColor = UIColor.clear
    tlabel.adjustsFontSizeToFitWidth = true
    tlabel.textAlignment = .center
    self.navigationItem.titleView = tlabel