ios - Auto-Stretching UITextField on typing -

i have uitextfield created programatically. want have uneditable prefixed characters on beginning , end, such

"hello [textfield] world".  

first, tried adding characters manually , using shouldchangecharactersinrange make approach won't work because if user long press on textfield , come beginning, can edit first characters (so can mess prefixed characters). option didn't seem convenient.

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another option creating empty uitextfield, , 2 static uilabels (for "hello" , "world"). here, problem arises. uitextfield's text center aligned (and vertically centered in view), giving width of view , 0 x-axis (so textfield touches both left , right edges of view). instead, if try give textfield fixed width while creating, width doesn't expand/stretch user types in.

what want achieve starting width of textfield 0, , having static uilabels on each sides "hello "[textfield]" world"; user types in, increasing/stretching textfield's width both left , right (as it's textaligned center). , textfield's width stretches, push uilabel's towards edge.. so:

|          ["hello "][textfield][" world"]         |  |    ["hello "][mytextfieldtextisnice][" world"]   | 

what proper way of achieving without using storyboard , programatically instantiating uitextfield , uilabels? how can create auto-resizing textfield user types in pushes uilabels on sides?

i use kind of situation,using storyboard , both side of uitextfield use uilabel center alignment.

below screenshot of storyboard.

then doing delegate of uitextfield , uses following code.

-(bool)textfield:(uitextfield *)textfield shouldchangecharactersinrange:(nsrange)range replacementstring:(nsstring *)string {      nsstring *strforwholestring = [nsstring stringwithformat:@"%@%@",textfield.text,string];      cgsize fontsize = [strforwholestring sizewithattributes:                        @{nsfontattributename:                              [uifont fontwithname:@"helvetica" size:14]}];        if (self.textfieldlayoutwidthconstraint.constant >= 40) {         self.textfieldlayoutwidthconstraint.constant = fontsize.width + 40 ;         [self.view layoutifneeded];         [self.view setneedsupdateconstraints];     }      return yes; } 

swift code

func textfield(textfield: uitextfield!, shouldchangecharactersinrange range: nsrange, replacementstring string: string!) -> bool {          let strforwholestring = nsstring(format:"%@%@", textfield.text!,string) string          let fontsize: cgsize = strforwholestring.sizewithattributes([nsfontattributename: uifont.systemfontofsize(14.0)])          if self.textfieldlayoutwidthconstraint?.constant >= 40 {             self.textfieldlayoutwidthconstraint!.constant = fontsize.width + 40 ;             self.view.layoutifneeded();             self.view.setneedsupdateconstraints();         }         return true     } 

may helps lot.

you can download sample code here - objective c

you can download sample code here - swift

output