ios - Getting height of UITableViewCell class without subclassing -

i'm trying calculate height of uitableviewcell without doing whole dance boundingrectwithsize.

here's approach:

+ (cgfloat)heightforitem:(id<ddinfoitem>)item {     if (!prototypecell)         prototypecell = [[nsbundle mainbundle] loadnibnamed:nsstringfromclass([self class]) owner:nil options:nil][0];      [prototypecell configureforitem:item];     [prototypecell layoutifneeded];      cgsize size = [prototypecell.contentview systemlayoutsizefittingsize:uilayoutfittingcompressedsize];     return size.height+1; } 

unfortunately, line

cgsize size = [prototypecell.contentview systemlayoutsizefittingsize:uilayoutfittingcompressedsize]; 

is returning nil... suspect because haven't set own constraints since not subclass of uitableviewcell. can confirm? there simple way of asking cell resize in situation?

thanks!

update

i still getting 0 height thought i've subclassed , added constraints in ib.

here's constraints on contentview in debugger:

<nslayoutconstraint:0x170091030 h:|-(nsspace(20))-[uilabel:0x12766b610]   (names: '|':uitableviewcellcontentview:0x178361380 )>, <nslayoutconstraint:0x170094370 v:|-(nsspace(20))-[uilabel:0x12766b610]   (names: '|':uitableviewcellcontentview:0x178361380 )>, <nslayoutconstraint:0x1700992d0 h:[uilabel:0x12766b610]-(nsspace(20))-|   (names: '|':uitableviewcellcontentview:0x178361380 )>, <nslayoutconstraint:0x170099500 v:[uilabel:0x12766b610]-(nsspace(8))-[uilabel:0x127559c20]>, <nslayoutconstraint:0x170099000 h:[uilabel:0x127559c20]-(nsspace(20))-|   (names: '|':uitableviewcellcontentview:0x178361380 )>, <nslayoutconstraint:0x17009c430 h:|-(nsspace(20))-[uilabel:0x127559c20]   (names: '|':uitableviewcellcontentview:0x178361380 )> 

note have replaced prototype cell's initwithstyle:identifier: nib loading method.

also, when log size of labels, indeed appear correctly resizing. result of calling systemlayoutsizefittingsize: still giving me 0 height :/

you're asking height in process. height 0 because @ point height has not been determined yet.