A simple domain-specific-language (DSL) for writing type-safe JSON in Swift
I wanted to implement a simple DSL in Swift 🙂
The result is a very lightweight API:
let json = JSON(
.array(
// 🚀 parses JSON encoded string and injects JSON elements
.json("[\"Developer\",{\"name\":\"crelies\",\"language\":\"swift\",\"iOS versions\":[8.0,9.0,10.0,11.0,12.0,13.0],\"projects\":{\"name\":\"AdvancedList\",\"developers\":[{\"name\":\"crelies\"}]}},\"Age\",29,\"Swift\",5.1,{\"isActive\":true},null]"),
"Developer",
.object(.property("name", "crelies"),
.property("language", "swift"),
.property("iOS versions", .array(8.0, 9.0, 10.0, 11.0, 12.0, 13.0)),
.property("projects", .object(.property("name", "AdvancedList"),
.property("developers", .array(.object(.property("name", "crelies"))))))
),
"Age",
29,
"Swift",
5.1,
.object(.property("isActive", true)),
nil
)
)
let renderedString = json.render()Output:
[
[
"Developer",
{
"name": "crelies",
"language": "swift",
"iOS versions": [
8.0,
9.0,
10.0,
11.0,
12.0,
13.0
],
"projects": {
"name": "AdvancedList",
"developers": [
{
"name": "crelies"
}
]
}
},
"Age",
29,
"Swift",
5.1,
{
"isActive": true
},
null
],
"Developer",
{
"name": "crelies",
"language": "swift",
"iOS versions": [
8.0,
9.0,
10.0,
11.0,
12.0,
13.0
],
"projects": {
"name": "AdvancedList",
"developers": [
{
"name": "crelies"
}
]
}
},
"Age",
29,
"Swift",
5.1,
{
"isActive": true
},
null
].json() you could end up with invalid JSON. You need to know if a JSON encoded string is allowed in a specific hierarchy (example: properties are not allowed in an array)!
When it comes to Strings it's getting complicated 💣
You can use
-
escaped JSON strings through
.json()(decodes string and injects JSON elements 🚀) or -
raw strings through
.raw("Test")or"Test"("Test"is shorthand syntax for.raw("Test")).
Hint: Keep in mind that you could get invalid JSON if you use an unescaped JSON string (see ❌ examples below).
Examples:
let json = JSON(
.array(
// ✅ parses JSON string and injects JSON elements
.json("[\"Developer\",{\"name\":\"crelies\",\"language\":\"swift\",\"iOS versions\":[8.0,9.0,10.0,11.0,12.0,13.0],\"projects\":{\"name\":\"AdvancedList\",\"developers\":[{\"name\":\"crelies\"}]}},\"Age\",29,\"Swift\",5.1,{\"isActive\":true},null]"),
// ########################################################################################
// ✅ raw strings, surrounding double quotes will be escaped
// - 1. Escaped characters
#"[\"Developer\",{\"name\":\"crelies\",\"language\":\"swift\",\"iOS versions\":[8.0,9.0,10.0,11.0,12.0,13.0],\"projects\":{\"name\":\"AdvancedList\",\"developers\":[{\"name\":\"crelies\"}]}},\"Age\",29,\"Swift\",5.1,{\"isActive\":true},null]"#,
// - 2. No escaped characters
#"Without escaped characters"#,
// ########################################################################################
// ✅ plain string
"Without escaped characters",
// ########################################################################################
/*
Not working because surrounding double quotes are not escaped.
(conflict with required JSON double quotes)
---> Will result in invalid JSON 💣
*/
// ❌
// "[\"Developer\",{\"name\":\"crelies\",\"language\":\"swift\",\"iOS versions\":[8.0,9.0,10.0,11.0,12.0,13.0],\"projects\":{\"name\":\"AdvancedList\",\"developers\":[{\"name\":\"crelies\"}]}},\"Age\",29,\"Swift\",5.1,{\"isActive\":true},null]"
// ########################################################################################
)
)Output:
[
[
"Developer",
{
"name": "crelies",
"language": "swift",
"iOS versions": [
8.0,
9.0,
10.0,
11.0,
12.0,
13.0
],
"projects": {
"name": "AdvancedList",
"developers": [
{
"name": "crelies"
}
]
}
},
"Age",
29,
"Swift",
5.1,
{
"isActive": true
},
null
],
"[\"Developer\",{\"name\":\"crelies\",\"language\":\"swift\",\"iOS versions\":[8.0,9.0,10.0,11.0,12.0,13.0],\"projects\":{\"name\":\"AdvancedList\",\"developers\":[{\"name\":\"crelies\"}]}},\"Age\",29,\"Swift\",5.1,{\"isActive\":true},null]",
"Without escaped characters",
"Without escaped characters"
]