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set a json value quickly

SJSON is a Go package that provides a very fast and simple way to set a value in a json document. The purpose for this library is to provide efficient json updating for the SummitDB project. For quickly retrieving json values check out GJSON.

Getting Started

Installing

To start using SJSON, install Go and run go get:

$ go get -u github.com/tidwall/sjson

This will retrieve the library.

Set a value

Set sets the value for the specified path. A path is in dot syntax, such as "name.last" or "age". This function expects that the json is well-formed and validated. Invalid json will not panic, but it may return back unexpected results. Invalid paths may return an error.

package main

import "github.com/tidwall/sjson"

const json = `{"name":{"first":"Janet","last":"Prichard"},"age":47}`

func main() {
	value, _ := sjson.Set(json, "name.last", "Anderson")
	println(value)
}

This will print:

{"name":{"first":"Janet","last":"Anderson"},"age":47}

Path syntax

A path is a series of keys separated by a dot. The dot and colon characters can be escaped with ''.

{
  "name": {"first": "Tom", "last": "Anderson"},
  "age":37,
  "children": ["Sara","Alex","Jack"],
  "fav.movie": "Deer Hunter",
  "friends": [
	{"first": "James", "last": "Murphy"},
	{"first": "Roger", "last": "Craig"}
  ]
}

"name.last"          >> "Anderson"
"age"                >> 37
"children.1"         >> "Alex"
"friends.1.last"     >> "Craig"

The -1 key can be used to append a value to an existing array:

"children.-1"  >> appends a new value to the end of the children array

Normally number keys are used to modify arrays, but it's possible to force a numeric object key by using the colon character:

{
  "users":{
    "2313":{"name":"Sara"},
    "7839":{"name":"Andy"}
  }
}

A colon path would look like:

"users.:2313.name"    >> "Sara"

Supported types

Pretty much any type is supported:

sjson.Set(`{"key":true}`, "key", nil)
sjson.Set(`{"key":true}`, "key", false)
sjson.Set(`{"key":true}`, "key", 1)
sjson.Set(`{"key":true}`, "key", 10.5)
sjson.Set(`{"key":true}`, "key", "hello")
sjson.Set(`{"key":true}`, "key", map[string]interface{}{"hello":"world"})

When a type is not recognized, SJSON will fallback to the encoding/json Marshaller.

Examples

Set a value from empty document:

value, _ := sjson.Set("", "name", "Tom")
println(value)

// Output:
// {"name":"Tom"}

Set a nested value from empty document:

value, _ := sjson.Set("", "name.last", "Anderson")
println(value)

// Output:
// {"name":{"last":"Anderson"}}

Set a new value:

value, _ := sjson.Set(`{"name":{"last":"Anderson"}}`, "name.first", "Sara")
println(value)

// Output:
// {"name":{"first":"Sara","last":"Anderson"}}

Update an existing value:

value, _ := sjson.Set(`{"name":{"last":"Anderson"}}`, "name.last", "Smith")
println(value)

// Output:
// {"name":{"first":"Sara","last":"Smith"}}

Set a new array value:

value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.2", "Sara")
println(value)

// Output:
// {"friends":["Andy","Carol","Sara"]

Append an array value by using the -1 key in a path:

value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.-1", "Sara")
println(value)

// Output:
// {"friends":["Andy","Carol","Sara"]

Append an array value that is past the end:

value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.4", "Sara")
println(value)

// Output:
// {"friends":["Andy","Carol",null,null,"Sara"]

Contact

Josh Baker @tidwall

License

SJSON source code is available under the MIT License.

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