如何在可选的字典数组中使用下标

Question

I am attempting to read a csv file on linux using the CSwiftV library, however the returned type that interests me the most is an optional array of dictionaries. I have been struggling to understand how to use subscripting to access the contents of the Array. Using the library most basic example (if you have marathon installed, just copy on a file and marathon run ):

import CSwiftV // marathon: https://github.com/Daniel1of1/CSwiftV.git

let inputString = "Year,Make,Model,Description,Price\r\n1997,Ford,E350,descrition,3000.00\r\n1999,Chevy,Venture,another description,4900.00\r\n"

let csv = CSwiftV(with: inputString)

let rows = csv.rows // [
                    //  ["1997","Ford","E350","descrition","3000.00"],
                    //  ["1999","Chevy","Venture","another description","4900.00"]
                    // ]

let headers = csv.headers // ["Year","Make","Model","Description","Price"]

let keyedRows = csv.keyedRows // [
                              //  ["Year":"1997","Make":"Ford","Model":"E350","Description":"descrition","Price":"3000.00"],
                              //  ["Year":"1999","Make":"Chevy","Model":"Venture","Description":"another, description","Price":"4900.00"]
                              // ]

print(csv.rows)
print(csv.headers)
print(csv.keyedRows)

So far so good, but now when I try print(csv.keyedRows[0][0]) or print(csv.keyedRows[[0]]) I get something like:

   - 24:16: value of optional type '[[String : String]]?' must be unwrapped to refer to member 'subscript' of wrapped base type '[[String : String]]'

• How can I access the dictionary data in this case (I am thinking on something similar to csv.keyedRows[0]["Year"] ) ?

Answer 1

For this:

print(csv.keyedRows[0]["Year"])

You can use optional binding:

if let keyedRows = csv.keyedRows {
    print(keyedRows[0]["Year"])
} else {
    // keyedRows is nil!
}

Or you can use the postfix ? operator:

print(csv.keyedRows?[0]["Year"] as Any)
// or
print(csv.keyedRows?[0]["Year"] ?? "")