How to append array on dictionary based on element exists

Question

On print po menuList?[1]["subMenu"]

I got below message

▿ Optional<Any>
  ▿ some : 1 element
    ▿ 0 : 1 element
      ▿ 0 : 2 elements
        - key : subItem
        ▿ value : 4 elements
          ▿ 0 : 7 elements
            ▿ 0 : 2 elements
              - key : permission
              - value : access
            ▿ 1 : 2 elements
              - key : title
              - value : Create
            ▿ 2 : 2 elements
              - key : bar
              - value : sidebar
            ▿ 3 : 2 elements
              - key : isNotify
              - value : 0
            ▿ 4 : 2 elements
              - key : link
              - value : linker
            ▿ 5 : 2 elements
              - key : path
              - value : /dashboard
            ▿ 6 : 2 elements
              - key : icon
              - value : add

Trying to extract menuList?[i]["subMenu"]["subItem"] based on condition if value exist in side subItem then append to array else not.

few cases ["subItem"] may have 0 elements

    if let permissionList =  MenuList?[i]["subMenu"] {
        let subMenu =  (permissionList as AnyObject)
        if subMenu.count > 0 {
            for j in 0..<subMenu.count{
             let subItem =  subMenu["subItem"]
            }
        }

Its return nil for me

On try subMenu[0] error: ambiguous use of 'subscript(_:)' subMenu[0]

What have you tried? How was the result different than what you expected? — jnpdx
– jnpdx, Commented Aug 3, 2021 at 1:16
In your sample data you printed, subItem only appears after two levels of arrays. Right now, it looks like you're just one level deep. — jnpdx
– jnpdx, Commented Aug 3, 2021 at 1:29
@kiran What's the type of menuList? It would help to figure this out. — George
– George, Commented Aug 3, 2021 at 1:46
@George_E var menuList: [[String: Any]]? its array of dictionary — kiran
– kiran, Commented Aug 3, 2021 at 1:47

Alexander · Accepted Answer · 2021-08-03 02:37:33Z

1

Here's a variant of George's function, expressing using a map operation rather than a hand-rolled loop:

func menuResult() -> [String] {
    // FIXME: Why is this even optional in the first place?
    guard let menuList = menuList else { return [] }

    return menuList.compactMap { menu -> [String] in
        guard let subMenu = menu["subMenu"] as? [String: String] else { return nil }
        return subMenu["subItem"]
    }
}

answered Aug 3, 2021 at 2:37

Alexander

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2 Comments

Leo Dabus Over a year ago

or simply (menu["subMenu"] as? [String: String])?["subItem"]. Single line is also preferred as it benefits type inference. Not sure but menuList?.compactMap { ($0["subMenu"] as? [String: String])?["subItem"] } ?? [] should work

Alexander Over a year ago

@LeoDabus Yep, though I avoided going that far because debugging that was really a pain. Maybe now that Xcode lets you place breakpoints within expressions, expressions like this might be more reasonable to work with

George · Accepted Answer · 2021-08-03 16:44:35Z

0

For example menuData like this:

let menuList: [[String: Any]]? = [
    ["abc": [
        "123": "test1",
        "456": "test2"
    ]],
    ["def": [
        "789": "test3",
        "101112": "test4"
    ]],
    ["subMenu": [
        "subItem": "Other correct path" // <- subMenu[2]["subMenu"]["subItem"]
    ]],
    ["subMenu": [
        "otherItem": "WRONG",
        "subItem": "CORRECT" // <- subMenu[3]["subMenu"]["subItem"]
    ]]
]

Code to get all items in the menuData array at menuData[i]["subMenu"]["subItem"]:

func menuResult() -> [String] {
    // menuList can't start nil
    guard let menuList = menuList else { return [] }
    var result = [String]()

    // Iterate every element of menuList
    for i in menuList.indices {
        // Get 'subMenu' dictionary if it exists
        if let subMenu = menuList[i]["subMenu"] as? [String: String] {
            // Get 'subItem' dictionary if it exists
            if let subItem = subMenu["subItem"] {
                // Store value at this path
                result.append(subItem)
            }
        }
    }

    return result
}

print(menuResult())
// Prints: ["Other correct path", "CORRECT"]

edited Aug 3, 2021 at 16:44

answered Aug 3, 2021 at 2:03

George

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8 Comments

Alexander Over a year ago

Your for loop can be replaced with a simple compactMap.

Alexander Over a year ago

Might I also suggest removing comment like // Return result when the code literally says return result. There should be a really high bar for what gets commented.

Alexander Over a year ago

I have some tips/tricks that might benefit this code, if you're interested. Would be easier to discuss them in SE chat, though

George Over a year ago

@Alexander Tbh, I think I just got a little bit carried away with the comments here 😅 Looking back it definitely has got quite a few inefficiencies (such as the index, not really neededP

Alexander Over a year ago

I don't use twitter, but I'd be happy to chat here. A chatroom link should be offered if we spam comments back and forth a few more times

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