How to access specific items in an array from Viper

Question

I have a yaml file similar to the following:

ComplexItemList:
- Name: First Complex item
  Date: Whenever
  StructItemList:
  - Name: blah
    Data1: 0
    Data2: Silly
  - Name: Yaddah
    Data1: 12
    Data2: Blah-blah-blah
- Name: Second Complex item
  Date: Yesterday
  StructItemList:
  - Name: blah
    Data1: 0
    Data2: Silly
  - Name: Yaddah
    Data1: 12
    Data2: Blah-blah-blah

Here is a simple version of my code:

package main

import (
    "fmt"

    "github.com/spf13/viper"
)

type StructItem struct {
    Name  string `yaml:"Name"`
    Data1 int    `yaml:"Data1"`
    Data2 string `yaml:"Data2"`
}

type ComplexItem struct {
    Name           string       `yaml:"Name"`
    Date           string       `yaml:"Date"`
    StructItemList []StructItem `yaml:"StructItemList,mapstructure"`
}

type TestConfig struct {
    Version         string        `yaml:"Version"`
    ComplexItemList []ComplexItem `yaml:"ComplexItemList,mapstructure"`
}

func main() {
    viper.SetConfigName("simple1") // name of config file (without extension)
    viper.SetConfigType("yaml")    // REQUIRED if the config file does not have the extension in the name
    viper.AddConfigPath(".")
    err := viper.ReadInConfig() // Find and read the config file
    if err != nil {             // Handle errors reading the config file
        panic(fmt.Errorf("Fatal error config file: %s \n", err))
    }

    test1 := viper.Get("ComplexItemList")
    fmt.Printf("test1:\n%#v\n", test1)
    // while I can easily unmarshal the information into a complex struct,
    // updating the file contents via viper does not seem straight forward.
    // Is there a way to access a specific item in an array using viper dot notation?

    config := TestConfig{}
    viper.Unmarshal(&config)
    // is the best way to update Data1 for "First Complex item", just to update the
    // unmarshalled struct then write the whole thing back out?
}

I want to use Viper to read the configuration file, but I'm unsure how to distinguish between "First Complex item" and "Second Complex item" when using the Get methods. Do I need to maintain state of the start of a complex item as they arrive?

Answer 1

I was over-complicating things. The easiest way is to unmarshal the values, update them, then Set the Array from the object.

    config := TestConfig{}
    viper.Unmarshal(&config)

    config.ComplexItemList[0].StructItemList[0].Data2 = "updated item"
    viper.Set("ComplexItemList", config.ComplexItemList)

Or is that not the correct way to handle updating the array in the yaml file via viper?