Swift 3 Equatable Struct optional function - swift

Question

This will be a little long winded so please bear with me. I am also a bit of a swift beginner as well. I have an array with a defined struct.
var modelOriginalArray = [model]()
struct model: Equatable {
var modelID = String()
var modelName = String()
var modelNumber = String()
var manufacturer = String()
var manufShort = String()
var phiTypeCode = String()
var phiTypeDesc = String()
init(modelID: String, modelName: String, modelNumber: String, manufacturer: String, manufShort: String, phiTypeCode: String, phiTypeDesc: String) {
self.modelID = modelID
self.modelName = modelName
self.modelNumber = modelNumber
self.manufacturer = manufacturer
self.manufShort = manufShort
self.phiTypeCode = phiTypeCode
self.phiTypeDesc = phiTypeDesc
}
static func == (lhs: model, rhs: model) -> Bool {
return lhs.manufShort == rhs.manufShort && lhs.modelName == rhs.modelName && lhs.modelNumber == rhs.modelNumber
}
}
I load about 5000 records into this array. I then have a need to filter this array based on search criteria. Let's say I am looking for a manufacturer "Sony". There is the possibility of multiple models for Sony so I need to separate all Sony records from the greater 5000.
srchval = "SONY"
var filteredArray = [model]()
var uniqueFilteredArray = [model]()
filteredArray = self.modelOriginalArray.filter { $0.manufShort.range(of: srchval, options: .caseInsensitive) != nil }
This will give me an array with only "Sony" records. However there is a possibility that some of those "Sony" records have duplicate manufShort, modelName, modelNumber values under different modelID's. I need to separate those and only have unique records.
// Find Uniquic options by removing duplicate Model Names
uniqueFilteredArray = unique(models: filteredArray)
func unique(models: [model]) -> [model] {
var uniqueModels = [model]()
for model in models {
if !uniqueModels.contains(model) {
uniqueModels.append(model)
}
}
return uniqueModels
}
This all works ver well. The problem I have is in the filter there are situations where I have to make sure the record is matching on:
static func == (lhs: model, rhs: model) -> Bool {
return lhs.manufShort == rhs.manufShort && lhs.modelName == rhs.modelName && lhs.modelNumber == rhs.modelNumber
}
And in a different situation in the same class I need to match only on the manufShort:
static func == (lhs: model2, rhs: model2) -> Bool {
return lhs.manufShort == rhs.manufShort
}
I have tried creating a separate model i.e.. model2 with this different static function, but I have difficulties moving data from one array to another with a different struct.
Any thoughts or a better way to accomplish this?
Thanks

Answer 1

Since you use two different approaches for defining the "equality" of two models, you should probably consider not using the == operator, as you don't really test equality if the equality predicate is different from case to case. Rather, you have two different custom predicates (which applies to two model instances) that you would like to use in different contexts. Why not use two custom type (static) methods for this, with descriptive names, semantically describing their different meanings?
Thanks! That makes a great deal of sense, how do I call the different (static) methods so that it will hit the right function based on what I am after. An example?
Example setup:
struct Foo {
let id: String
let bar: Int
let baz: Int
let bax: Int
init(_ id: String, _ bar: Int, _ baz: Int, _ bax: Int)
{
self.id = id
self.bar = bar
self.baz = baz
self.bax = bax
}
static func byBarEqualityPredicate(lhs: Foo, rhs: Foo) -> Bool {
return lhs.bar == rhs.bar
}
static func byBazAndBaxEqualityPredicate(lhs: Foo, rhs: Foo) -> Bool {
return lhs.baz == rhs.baz && lhs.bax == rhs.bax
}
}
let fooArr = [Foo("Foo A", 1, 2, 3),
Foo("Foo B", 1, 1, 2),
Foo("Foo C", 3, 1, 2)]
A slightly modified version of your unique method, now supplying a (Foo, Foo) -> Bool predicate among with the foos array:
func unique(foos: [Foo], predicate: (Foo, Foo) -> Bool) -> [Foo] {
var uniqueFoos = [Foo]()
for foo in foos {
if !uniqueFoos.contains(where: { predicate($0, foo) }) {
uniqueFoos.append(foo)
}
}
return uniqueFoos
}
Testing with the two different Foo predicates:
// by 'bar' "equality": Foo A and Foo B will be considered "equal",
// and only Foo A, among these two , will be added to the "unique" array.
let fooWithBarPredicate = unique(foos: fooArr, predicate: Foo.byBarEqualityPredicate)
fooWithBarPredicate.forEach { print($0.id) } // Foo A, Foo C
// by 'baz' && 'bax' "equality": Foo A and Foo C will be considered "equal",
// and only Foo A, among these two, will be added to the "unique" array.
let fooWithBazBaxPredicate = unique(foos: fooArr, predicate: Foo.byBazAndBaxEqualityPredicate)
fooWithBazBaxPredicate.forEach { print($0.id) } // Foo A, Foo B

Answer 2

You can use the following extension on Collection. Not tested.
extension Collection where Iterator.Element: Equatable {
func uniques(by equals: (Iterator.Element, Iterator.Element) -> Bool) -> [Iterator.Element] {
var uniqueElems: [Iterator.Element] = []
for elem in self {
if uniqueElems.index(where: { equals($0, elem) }) == nil {
uniqueElems.append(elem)
}
}
return uniqueElems
}
}
Then you can use
filteredArray.uniques { $0.manufShort == $1.manufShort }
filteredArray.uniques { $0.manufShort == $1.manufShort && $0.modelName == $1.modelName && $0.modelNumber == $1.modelNumber }