这是我认为你想要的：

// All of the different flavours in myIcecreams as a Set to remove
// duplicates and increase performance of looking up flavours
// ["banana", "mint", "chocolate"]
let myFlavours = Set(myIcecreams.map { $0.flavour })

// All entries from `shopIcecreams` with a flavour not in `myFlavours`
let filteredIcecreams = shopIcecreams.filter { shopIcecream in
    !myFlavours.contains(shopIcecream.flavour)
}

struct Icecream: Encodable, Decodable {
    var color: String
    var flavour: String
}

var myIcecreams = [
    Icecream(color: "yellow", flavour: "banana"),
    Icecream(color: "green", flavour: "mint"),
    Icecream(color: "white", flavour: "banana"),
    Icecream(color: "brown", flavour: "chocolate")
]

var shopIcecreams = [
    Icecream(color: "red", flavour: "strawberry"),
    Icecream(color: "purple", flavour: "blueberry"),
    Icecream(color: "green", flavour: "pistachio"),
    Icecream(color: "white", flavour: "chocolate")
]

var newArray: [Icecream] = []

for i in shopIcecreams {
    var match = false
    for j in myIcecreams {
        if i.flavour == j.flavour {
            match = true
            break
        }
        else {
            match = false
        }
    }
    if match == false {
        newArray.append(i)
    }
}

// Printing new array
for i in newArray {
    print(i)
}

Click Here to see the output

输出：

冰淇淋（颜色：“红色”，风味：“草莓”）冰淇淋（颜色：“紫”，味：“蓝莓”）冰淇淋（颜色：“绿色”，风味：“开心果”）