Parse JSON from mixed array with Decodable Swift

First, I'm assuming this is the data structure you want. If it's not, please update the question with your expected output data structure. (report[0][0].name is fragile and awkward to use in Swift. Create a struct that matches the data you would like to have. Then decode into that struct.)

struct ApiData: Decodable {
    let report: [Details]
}

struct Details {
    let name: String
    let value1: Int
    let value2: Int
}

So each Details has exactly a name object and two integer values. And a report is a list of Details.

given that, you can hand-decode Details using a unkeyedContainer. To get the name field out, it is handy to make a helper struct:

extension Details: Decodable {
    struct NameField: Decodable {
        let name: String
    }

    init(from decoder: Decoder) throws {
        var container = try decoder.unkeyedContainer()
        self.name = try container.decode(NameField.self).name
        self.value1 = try container.decode(Int.self)
        self.value2 = try container.decode(Int.self)
    }
}

Your comment notes "there is some more below name." In that case, you may want an object rather than a string here. In that case, it would look like this:

struct Person: Decodable {
    let name: String
}

struct Details {
    let person: Person
    let value1: Int
    let value2: Int
}

extension Details: Decodable {

    init(from decoder: Decoder) throws {
        var container = try decoder.unkeyedContainer()
        self.person = try container.decode(Person.self)
        self.value1 = try container.decode(Int.self)
        self.value2 = try container.decode(Int.self)
    }
}

Finally, it's possible that the list of values is unbounded, and you want an array:

struct Details {
    let person: Person
    let values: [Int]
}

In that case you'd decode by extracting all the values out of the unkeyedContainer:

extension Details: Decodable {    
    init(from decoder: Decoder) throws {
        var container = try decoder.unkeyedContainer()
        self.person = try container.decode(Person.self)
        var values: [Int] = []
        while !container.isAtEnd {
            values.append(try container.decode(Int.self))
        }
        self.values = values
    }
}

There are lots of ways to approach this. It all depends on how you want to use the data, and how much structure the data has.