Unmarshalling JSON with Nesting and Structural Similarity
When dealing with complex JSON structures, it is common to encounter scenarios where one element of a struct is of the same type as the struct itself. This can pose challenges during the unmarshalling process.
In this specific case, we are given a JSON string that represents an array of database configurations. Each database configuration contains various attributes, including a list of replicas. Each replica is also a JSON object with attributes similar to the database configuration.
To unmarshal this JSON string, we need a data structure that can accommodate the nesting and structural similarity.
Modeling the Nested Structure with Dynamic Types
Since the JSON input is not a slice of DBS structs, we need a more flexible data type to capture its structure. A map[string]interface{} is an excellent option because it can represent key-value pairs with dynamic values.
Example:
type DBS struct { URL string Port string Uname string Pass string Authdb string Replicas []DBS } func main() { raw, err := ioutil.ReadFile("./config.json") if err != nil { fmt.Println(err.Error()) os.Exit(1) } var config []map[string]interface{} json.Unmarshal(raw, &config) for _, db := range config { d, ok := db["db"] if !ok { // Handle the case where "db" is missing } db := d.(map[string]interface{}) url := db["url"].(string) port := db["port"].(string) var replicas []DBS for _, replica := range db["replicas"] { replicas = append(replicas, mapToDBS(replica)) } // ... Other operations } }
Using a Dynamic Type to Parse the JSON
In this example, the config variable is a slice of maps, which allows it to hold the database configurations as key-value pairs.
For each database configuration, we retrieve the "db" sub-object and cast it to a map[string]interface{}. This allows us to access the individual attributes such as "url" and "port".
The "replicas" attribute is handled similarly. Each replica is a JSON object, so it can be converted into a DBS struct using the mapToDBS() function.
By leveraging the flexibility of dynamic types, we can effectively unmarshal the JSON string and parse its nested structure.
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