Apply map to JSON array in swift

Question

Using SwiftyJSON I loaded a JSON array with the following structure.

 [
  {
  "x": 2,
  "y": 2,
  "r": 100,
  "description": {"name":"bob","institution":"NYU","technologies":[]}
  },
  {
  "x": 4,
  "y": 4,
  "r": 200,
  "description": {"name":"bob","institution":"NYU","technologies":[]}  },...
]

Problem

I want to create an object from each element in this array.

My approach

    let chartPoints: [ChartPointBubble] = json.array.map{
        ChartPointBubble(x: ChartAxisValueFloat(CGFloat($0.x), labelSettings:labelSettings),
            y:ChartAxisValueFloat(CGFloat($0.y)), diameterScalar: $0.r, description: $0.description)
    }

The error

Cannot invoke map with an argument of list type ((_) -> _)

Mikael Hellman · Accepted Answer · 2015-05-29 22:21:17Z

1

Updated, not closure.

var chartPoints = [ChartPointBubble]()
for (index: String, subJson: JSON) in json {
   let pointBubble = ChartPointBubble(
        x: ChartAxisValueFloat(CGFloat(subJson.x.int),  
        labelSettings:labelSettings),
        y:ChartAxisValueFloat(CGFloat(subJson.y.int)), 
        diameterScalar: subJson.r.int, 
        description: subJson.description)

    chartPoints.append(pointBubble)
}

EDIT: I took a look at the docs. Think best approach is to loop it. Also, not sure of type for your: ChartAxisValueFloat.description.

edited May 29, 2015 at 22:21

answered May 29, 2015 at 21:36

Mikael Hellman

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5 Comments

mac389 Over a year ago

The README (github.com/SwiftyJSON/SwiftyJSON/blob/master/README.md) suggests the type is JSON

mac389 Over a year ago

This gives me the error, cannot invoke map of argument list with type ((JSON) --> ChartPointBubble)

mac389 Over a year ago

ChartAxisValueFloat.description is itself a JSON array, as indicated in the OP.

Mikael Hellman Over a year ago

In that case the code above should probably work... :)

mac389 Over a year ago

I think you mixed object and subJson

jneighbs · Accepted Answer · 2015-05-29 22:09:35Z

The error is pointing out the fact that you are passing a closure of type ()->() into the array's 'map' method. In this case, the map method needs to receive an argument of type (whateverTypeIsAlreadyInTheArray) -> (ChartPointBubble).

You might be able to fix this by:

adding the line "(var arrayItem) -> ChartPointBubble in" right after the first open curly brace found after the method 'map'. (I'm pretty sure you don't have to specify the type of arrayItem as it can be inferred from the items already in the array)
replacing '$0' with 'arrayItem'
returning the new ChartPointBubble you are creating

Edit: - final code should look like this

let chartPoints: [ChartPointBubble] = json.array.map{
    (var arrayItem) -> ChartPointBubble in
        return ChartPointBubble(
            x: ChartAxisValueFloat(CGFloat(arrayItem.x),  
            labelSettings:labelSettings),
            y:ChartAxisValueFloat(CGFloat(arrayItem.y)), 
            diameterScalar: object.r, 
            description: object.description)
}

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