dig

Package dig provides tools for traversing Go maps. dig turns this:

foo = myMap["a"].(map[string]interface{})["b"].(map[string]interface{})["c"].(uint64)

into this:

foo = dig.Uint64(myMap, "a", "b", "c")

Useful when you depend on external services, such as web-APIs, and you don't really want to handle all possible error cases or possible panic points caused by sudden changes on the expected JSON.

Installation

go get -u github.com/xiam/dig

Usage

Start with a map[string]interface{} and define which path to follow, take this testMap example:

testMap := map[string]interface{}{
	"first": map[string]interface{}{
		"first.1": map[string]string{
			"col.1": "a",
			"col.2": "b",
			"col.3": "c",
		},
	},
	"second": map[string]map[string]string{
		"second.2": map[string]string{
			"col.4": "d",
			"col.5": "e",
			"col.6": "f",
		},
	},
}

suppose you want to get the value of the element with key "col.4". You'll need a path, the path of a node is defined as the array of map keys that you need to traverse in order to get to that node, in the above example the path would be: second > second.2 > col.4, in that specific order.

Now suppose you expect "col.4" to be a string, then you'd use dig.String() to get the value.

// s = "d"
s := dig.String(&testMap, "second", "second.2", "col.4")

Note that you're passing a pointer to map (&testMap) instead of a map.

There are more sugar methods with similar functionality, such as dig.Uint64(), dig.Float64(), dig.Interface(), etc. all these methods will attempt to convert the node data type into the expected Go type.

The dig.String() function and friends are just wrappers around dig.Get(), and you can also use dig.Get() to get a node value, it will also produce an error value if something goes wrong.

var s string
err := dig.Get(&testMap, &s, "second", "second.2", "col.4")

Now suppose you'd like to set the value of "col.5", you'd use the dig.Set() function:

dig.Set(&testMap, "modified", "second", "second.2", "col.4")

And finally, if you're ever in the need of creating a route on a map, you could use dig.Dig() like this:

var i int

m := map[string]interface{}{}

// Create a path.
dig.Dig(&m, "foo", "bar", "baz")

// Set the value 42.
dig.Set(&m, 42, "foo", "bar", "baz")

// Get the value, expecting 42.
dig.Get(&m, &i, "foo", "bar", "baz")

if i != 42 {
	t.Errorf("Test failed.")
}

Please consult the online documentation to get a list of all available methods.

Documentation

See the online docs.

License

Copyright (c) 2013-today José Nieto, https://xiam.dev

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.