A native Swift JsonLogic implementation. This parser accepts JsonLogic rules and executes them.
JsonLogic is a way to write rules that involve computations in JSON format, these can be applied on JSON data with consistent results. So you can share between server and clients rules in a common format. Original JS JsonLogic implementation is developed by Jeremy Wadhams.
To use the pod in your project add in the Podfile:
pod jsonlogic
To run the example project, just run:
pod try jsonlogic
if you use Swift Package Manager add the following in dependencies:
dependencies: [
.package(
url: "https://github.com/advantagefse/json-logic-swift", from: "1.0.0"
)
]
You simply import the module and either call the applyRule global method:
import jsonlogic
let rule =
"""
{ "var" : "name" }
"""
let data =
"""
{ "name" : "Jon" }
"""
//Example parsing
let result: String? = try? applyRule(rule, to: data)
print("result = \(String(describing: result))")The applyRule will parse the rule then apply it to the data and try to convert the
result to
the
inferred return
type,
if it fails an error will be thrown.
If you need to apply the same rule to multiple data then it will be better to parse the rule once.
You can do this by initializing a JsonRule object with the rule and then calling
applyRule.
//Example parsing
let jsonlogic = try JsonLogic(rule)
var result: Bool = jsonlogic.applyRule(to: data1)
result = jsonlogic.applyRule(to: data2)
//etc..let rule = """
{ "==" : [1, 1] }
"""
let result: Bool = try applyRule(rule)
//evaluates to trueThis is a simple test, equivalent to 1 == 1. A few things about the format:
- The operator is always in the "key" position. There is only one key per JsonLogic rule.
- The values are typically an array.
- Each value can be a string, number, boolean, array (non-associative), or null
Here we're beginning to nest rules.
let rule = """
{"and" : [
{ ">" : [3,1] },
{ "<" : [1,3] }
] }
"""
let result: Bool = try applyRule(rule)
//evaluates to trueIn an infix language this could be written as:
( (3 > 1) && (1 < 3) )Obviously these rules aren't very interesting if they can only take static literal data.
Typically jsonLogic will be called with a rule object and a data object. You can use the var
operator to get attributes of the data object:
let rule = """
{ "var" : ["a"] }
"""
let data = """
{ a : 1, b : 2 }
"""
let result: Int = try applyRule(rule, to: data)
//evaluates to 1If you like, we support to skip the array around values:
let rule = """
{ "var" : "a" }
"""
let data = """
{ a : 1, b : 2 }
"""
let result: Int = try applyRule(rule, to: data)
//evaluates to 1You can also use the var operator to access an array by numeric index:
jsonLogic.apply(
{"var" : 1 },
[ "apple", "banana", "carrot" ]
);
// "banana"Here's a complex rule that mixes literals and data. The pie isn't ready to eat unless it's cooler than 110 degrees, and filled with apples.
let rule = """
{ "and" : [
{"<" : [ { "var" : "temp" }, 110 ]},
{"==" : [ { "var" : "pie.filling" }, "apple" ] }
] }
"""
let data = """
{ "temp" : 100, "pie" : { "filling" : "apple" } }
"""
let result: Bool = try applyRule(rule, to: data)
//evaluates to trueYou can register a custom operator
import jsonlogic
import JSON
// the key is the operator and the value is a closure that takes as argument
// a JSON and returns a JSON
let customRules =
["numberOfElementsInArray": { (json: JSON?) -> JSON in
switch json {
case let .Array(array):
return JSON(array.count)
default:
return JSON(0)
}
}]
let rule = """
{ "numberOfElementsInArray" : [1, 2, 3] }
"""
// The value is 3
let value: Int = try JsonLogic(rule, customOperators: customRules).applyRule()For a complete list of the supported operators and their usages see jsonlogic operators.
Comming soon...
Making changes are welcome. If you find a bug please submit a unit test that reproduces it, before submitting the fix.
Because the project was created and build using the Swift PM there is no Xcode project file
committed in the repo. If you need one you can generated by running genenate-xcodeproj.sh
in the terminal:
$ . generate-xcodeproj.sh
| iOS | tvOS | watchOS | macOS |
|---|---|---|---|
| >=9.0 | >=10.0 | >=2.0 | >=10.12 |
Christos Koninis, c.koninis@afse.eu
JsonLogic for Swift is available under the MIT license. See the LICENSE file for more info.