How do I concisely update a highly nested object model using swift? - arrays

Question

I am writing a function which will dig into the deepest level of a object hierarchy and update a particular value. For reference, this is how messy a regular iteration turned out to be:
func selectedStateUpdated(data: MyObject, tabId: String, rowId: String){
for currIndex in 0..<self.model.data[0].data[0].filters.count{
if(self.model.data[0].data[0].filters[currIndex].headerName == data.headerName){
for tabIdx in 0..<model.data[0].data[0].filters[currIndex].data.count {
if(self.model.data[0].data[0].filters[currIndex].data[tabIdx].id == tabId){
for rowItemIdx in 0..<self.model.data[0].data[0].filters[currIndex].data[tabIdx].data.count {
if(self.model.data[0].data[0].filters[currIndex].data[tabIdx].data[rowItemIdx].id == rowId){
self.model.data[0].data[0].filters[currIndex].data[tabIdx].data[rowItemIdx].isSelected.toggle()
}
}
}
}
}
}
}
What is the best way to dig this deep into my data model and update a particular attribute? I am trying to update the model object which resides in the class of this function as a global object. Given that iterable objects in my object model are immutable in for-loops, is there a better way of approaching this while making sure I iterated into the proper

Answer 1

At its core, this is a data structure problem. You're doing a linear search through all your data to find something with a specific headerName, tabId, rowId. It's complicated, messy and slow (O(headerCount * tabCount * rowCount)!)
If dictionaries were used, this could just be:
self.model.data[0].data[0]
.filters[headerName]
.data[tabId]
.data[rowId]
.isSelected
.toggle()
If the arrays must stay, then you can clean this up a lot by extracting common parts to named local variables. Inverting the if statements (in this case, into guard statements`) also saves a ton on nesting:
func selectedStateUpdated(headerName: String, tabId: String, rowId: String){
let data = self.model.data[0].data[0] // TODO: name me better
for currIndex in 0..<data.filters.count {
let filter = data.filters[currIndex]
guard filter.headerName == headerName else { return }
for tabIdx in 0..<filter.data.count {
let tab = filter.data[tabIdx]
guard tab.id == tabId else { continue }
for rowItemIdx in 0..< tab.data.count {
let rowItem = tab.data[rowItemIdx]
guard rowItem.id == rowId else { continue }
self.model.data[0].data[0]
.filters[currIndex]
.data[tabIdx]
.data[rowItemIdx]
.isSelected
.toggle()
}
}
}
}
It could be further improved by using zip to get indices and items in one shot:
func selectedStateUpdated(headerName: String, tabId: String, rowId: String){
let data = self.model.data[0].data[0] // TODO: name me better
for (currIndex, filter) in zip(data.filters.indices, data.filters) {
guard filter.headerName == headerName else { return }
for (tabIdx, tab) in zip(filter.data.indices, filter.data) {
guard tab.id == tabId else { continue }
for (rowItemIdx, rowItem) in zip(tab.data.indices, tab.data) {
guard rowItem.id == rowId else { continue }
self.model.data[0].data[0]
.filters[currIndex]
.data[tabIdx]
.data[rowItemIdx]
.isSelected
.toggle()
}
}
}
}

Answer 2

Basically what you are doing when you say ".id == tabId" is a filter function. This code was quite messy. But i think i managed to figure it out:
func selectedStateUpdated(data: [MyObject], tabId: String, rowId: String) {
let filteredResult = self.model.data[0].data[0].filters
.filter({$0.headerName == data.headerName &&
$0.data.filter({$0.id == tabId}) &&
$0.data.filter({$0.id == tabId &&
$0.data.filter({$0.id == rowId})
})
})
if filteredResult.count > 0 {
filteredResult.first!.isSelected.toggle()
}
}