Added doc entry on nested key access

This commit is contained in:
Kiril Zvezdarov 2015-05-02 14:20:33 -04:00
parent 8d9577a72e
commit 2e47d9ed4a

View file

@ -237,6 +237,71 @@ Example:
fmt.Println("verbose enabled") fmt.Println("verbose enabled")
} }
### Accessing nested keys
The accessor methods also accept formatted paths to deeply nested keys.
For example, if the following JSON file is loaded:
```
{
"host": {
"address": "localhost",
"port": 5799
},
"datastore": {
"metric": {
"host": "127.0.0.1",
"port": 3099
},
"warehouse": {
"host": "198.0.0.1",
"port": 2112
}
}
}
```
Viper can access a nested field by passing a `.` delimited path of keys:
```
GetString("datastore.metric.host") // (returns "127.0.0.1")
```
This obeys the precendense rules established above; the search for the root key
(in this examole, `datastore`) will cascade through the remaining configuration registries
until found. The search for the subkeys (`metric` and `host`), however, will not.
For example, if the `metric` key was not defined in the configuration loaded
from file, but was defined in the defaults, Viper would return the zero value.
On the other hand, if the primary key was not defined, Viper would go through the
remaining registries looking for it.
Lastly, if there exists a key that matches the delimited key path, its value will
be returned instead. E.g.
```
{
"datastore.metric.host": "0.0.0.0",
"host": {
"address": "localhost",
"port": 5799
},
"datastore": {
"metric": {
"host": "127.0.0.1",
"port": 3099
},
"warehouse": {
"host": "198.0.0.1",
"port": 2112
}
}
}
GetString("datastore.metric.host") //returns "0.0.0.0"
```
### Marshaling ### Marshaling
You also have the option of Marshaling all or a specific value to a struct, map, etc. You also have the option of Marshaling all or a specific value to a struct, map, etc.