i'm trying reordered index of cells array.
in viewdidload
cell.showsreordercontrol = yes; arraytag = [nsmutablearray array]; //saving indexpath.row cell.tag while creating cell.
- (uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath { ..... cell.tag = indexpath.row; nsstring *strcelltag = [nsstring stringwithformat:@"%d",cell.tag]; if(![arraytag containsobject:strcelltag]) { [arraytag addobject:strcelltag]; } return cell; } //i'm not sure if right way, below i'm trying save changes array.
- (nsindexpath *)tableview:(uitableview *)tableview targetindexpathformovefromrowatindexpath:(nsindexpath *)sourceindexpath toproposedindexpath:(nsindexpath *)proposeddestinationindexpath { [arraytag replaceobjectatindex:sourceindexpath.row withobject:[nsstring stringwithformat:@"%i",proposeddestinationindexpath.row]]; [arraytag replaceobjectatindex:proposeddestinationindexpath.row withobject:[nsstring stringwithformat:@"%i",sourceindexpath.row]]; return proposeddestinationindexpath; } to verify nslog:
- (ibaction)donebutton:(id)sender { nslog (@"number of objects in array %i", arraytag.count); (nsstring *obj in arraytag){ nslog(@"from arraytag obj: %@", obj); } } nslog without moving cells results expected.
2013-07-10 17:50:47.291 myapp[1634:c07] number of objects in array 7 2013-07-10 17:50:47.292 myapp[1634:c07] arraytag obj: 0 2013-07-10 17:50:47.292 myapp[1634:c07] arraytag obj: 1 2013-07-10 17:50:47.292 myapp[1634:c07] arraytag obj: 2 2013-07-10 17:50:47.292 myapp[1634:c07] arraytag obj: 3 2013-07-10 17:50:47.293 myapp[1634:c07] arraytag obj: 4 2013-07-10 17:50:47.293 myapp[1634:c07] arraytag obj: 5 2013-07-10 17:50:47.293 myapp[1634:c07] arraytag obj: 6 nslog after moving/shuffling cells appears wrong. i'm not getting unique values.
2013-07-10 17:51:55.329 myapp[1634:c07] number of objects in array 7 2013-07-10 17:51:55.330 myapp[1634:c07] arraytag obj: 4 2013-07-10 17:51:55.330 myapp[1634:c07] arraytag obj: 5 2013-07-10 17:51:55.330 myapp[1634:c07] arraytag obj: 5 2013-07-10 17:51:55.330 myapp[1634:c07] arraytag obj: 5 2013-07-10 17:51:55.331 myapp[1634:c07] arraytag obj: 6 2013-07-10 17:51:55.331 myapp[1634:c07] arraytag obj: 6 2013-07-10 17:51:55.331 myapp[1634:c07] arraytag obj: 4 q: why not getting new unique values after reordering? how new order of cells saved in array?
delegate , datasource clarification
you shouldn't modify data behind tableview during:
-tableview:targetindexpathformovefromrowatindexpath:toproposedindexpath: this method gets called when user hovering cell above others, , thus, causes multiple calls function while cell being dragged.
the key here that, method part of uitableviewdelegate, it's not meant modify data, change appearence of tableview, , it's there "sliding" animation when cell hovering. returned value determines cell should animated to.
what should do, perform changes when user has commited them, happens when call uitableviewdatasource protocol method:
-tableview:moverowatindexpath:toindexpath: this when user has released cell , it's on place, , occurs once per drag & drop.
as general rule of thumb, whatever on uitableviewdelegate shows, , what's on uitableviewdatasource real data.
modifying model
swapping
swapping or exchanging, easiest case ([a, b, c, d] => [d, b, c, a]), , there's convenient method that:
[arraytag exchangeobjectatindex:fromindexpath.row withobjectatindex:toindexpath.row]; swift
let f = fromindexpath.row, t = toindexpath.row (array[f], array[t]) = (array[t], array[f]) insertion
insertion little more tricky , verbose ([a, b, c, d] => [b, c, d, a]). important thing making changes don't affect each other.
id obj = [arraytag objectatindex:fromindexpath.row]; [arraytag removeobjectatindex:fromindexpath.row]; [arraytag insertobject:obj atindex:toindexpath.row]; swift
let obj = array.removeatindex(fromindexpath.row) array.insert(newelement: obj, atindex: toindexpath.row) 
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