iphone - NSClassFromString - doesn't work -

i'm trying use dynamic typing in obj-c, i've got following code , errors:

for me seems good, don't want work, ideas?

since not creating new instance (just retrieving one), there no need this. sufficient:

// if don't know exact class of cell, type common superclass of cells uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:@"rssitemcell"];