ios - getting the height of a label in custom cell to use for heightForRowAt in my main view controller -

i have view controller uses custom cell called searchcell bring content in , wondering how can height of label lblleft , use in tableview(_ tableview: uitableview, heightforrowat indexpath: indexpath) -> cgfloat function return height of label. code i'm using in main view controller:

func tableview(_ tableview: uitableview, cellforrowat indexpath:      indexpath) -> uitableviewcell {     if searchmode == searching {         let cell: mhsearchcell = tableview.dequeuereusablecell(withidentifier:          mhsearchcell.reusableidentifier()) as! mhsearchcell          cell.helper = helpers[indexpath.row]         cell.delegate = self          return cell   } } 

part of code creates label in mhsearchcell, label connected here iboutlet:

lblleft.text = ""          if let expertisecount = helper.expertise {              let paragraphstyle = nsmutableparagraphstyle()             paragraphstyle.linespacing = 5             paragraphstyle.linebreakmode = .bywordwrapping             paragraphstyle.alignment = nstextalignment.center             lblleft.numberoflines = 0              let finalstring = expertisecount.map({$0.name!}).joined(separator: "   \u{00b7}   ")             let finalattributedstring = nsmutableattributedstring(string: finalstring, attributes: [nsparagraphstyleattributename:paragraphstyle])             lblleft.attributedtext = finalattributedstring         } 

i use custom extension calculate height of nsattributedstring. "containerwidth" max width of label, contentview.bounds.size.width of cell.

extension nsattributedstring {  func height(containerwidth: cgfloat) -> cgfloat {     let rect = self.boundingrect(with: cgsize.init(width: containerwidth, height: cgfloat.greatestfinitemagnitude), options: [.useslinefragmentorigin, .usesfontleading], context: nil)     return ceil(rect.size.height) }  func width(containerheight: cgfloat) -> cgfloat {     let rect = self.boundingrect(with: cgsize.init(width: cgfloat.greatestfinitemagnitude, height: containerheight), options: [.useslinefragmentorigin, .usesfontleading], context: nil)     return ceil(rect.size.width) } 

}

one "trick" heightforrowatindexpath called before cellforrowatindexpath. need create placeholder cell , keep reference it. this:

// init once , var searchcellplaceholder = searchcell() // use whatever default initializer   func tableview(_ tableview: uitableview, heightforrowat indexpath: indexpath) -> cgfloat {     let object = data[indexpath.row]     // keep reusing cell , populate new object text, use configure method in cellforrowatindex too.     configurecell(cell: searchcellplaceholder object: object)     // height of label after text applied     let height = searchcell.label.height(containerwidth: serachcell.contentview.bounds.size.width)      return height } 

you don't want init placeholder cell in heightforrowatindexpath because kill performance initialize object every time that's called. that's why initialize beginning , keep reusing it.

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if you're using auto layout, can how have uitableview automatically set height of cell you. better option.