jsonnet入门
2020-07-23 本文已影响0人
wwq2020
jsonnet 是 Google 推出的一门 JSON 模板语言.
编译器
定义变量
编写 demo.jsonnet,内容如下
local data = 1;
{
data: data,
}
执行
jsonnet demo.jsonnet > demo.json
输出
{
"data": 1
}
引用
self 指向当前对象
$指向最外部对象
["name"]查找 field
.name 如果 name 是标识符
[1] 查找数组元素
local array = [1,2,3];
{
"data1": array[1],
"data2": self.data1,
"data3": {
data: $.data1,
},
"data4": {
data: $["data3"].data,
},
}
执行
jsonnet demo.jsonnet > demo.json
输出
local array = [1,2,3];
{
"data1": array[1],
"data2": self.data1,
"data3": {
data: $.data1,
},
"data4": {
data: $["data3"].data,
},
}
算术
编写 demo.jsonnet,内容如下
{
concat_array: [1, 2, 3] + [4],
concat_string: '123' + 4,
equality1: 1 == '1',
equality2: [{}, { x: 3 - 1 }]
== [{}, { x: 2 }],
ex1: 1 + 2 * 3 / (4 + 5),
// 位操作,首先转为int
ex2: self.ex1 | 3,
// 取模
ex3: self.ex1 % 2,
// 逻辑操作
// Boolean logic
ex4: (4 > 3) && (1 <= 3) || false,
// 对象混合
// Mixing objects together
obj: { a: 1, b: 2 } + { b: 3, c: 4 },
// 测试field是否在对象内
obj_member: 'foo' in { foo: 1 },
// 字符串格式化
str1: 'The value of self.ex2 is '
+ self.ex2 + '.',
str2: 'The value of self.ex2 is %g.'
% self.ex2,
str3: 'ex1=%0.2f, ex2=%0.2f'
% [self.ex1, self.ex2],
// 传入self,ex1和ex2内部提取
str4: 'ex1=%(ex1)0.2f, ex2=%(ex2)0.2f'
% self,
// 对整个文件进行文本模板化
str5: |||
ex1=%(ex1)0.2f
ex2=%(ex2)0.2f
||| % self,
}
执行
jsonnet demo.jsonnet > demo.json
输出
{
"concat_array": [
1,
2,
3,
4
],
"concat_string": "1234",
"equality1": false,
"equality2": true,
"ex1": 1.6666666666666665,
"ex2": 3,
"ex3": 1.6666666666666665,
"ex4": true,
"obj": {
"a": 1,
"b": 3,
"c": 4
},
"obj_member": true,
"str1": "The value of self.ex2 is 3.",
"str2": "The value of self.ex2 is 3.",
"str3": "ex1=1.67, ex2=3.00",
"str4": "ex1=1.67, ex2=3.00",
"str5": "ex1=1.67\nex2=3.00\n"
}
函数
编写 demo.jsonnet,内容如下
local demo(x, y=1) = x + y;
{
data: demo(1),
}
执行
jsonnet demo.jsonnet > demo.json
输出
{
"data": 2
}
条件
编写 demo.jsonnet,内容如下
local demo(flag) =
if flag then 'hello' else 'world';
{
data1: demo(true),
data2: demo(false),
}
执行
jsonnet demo.jsonnet > demo.json
输出
{
"data1": "hello",
"data2": "world"
}
数组和对象
编写 demo.jsonnet,内容如下
local arr = std.range(5, 8);
{
array_comprehensions: {
higher: [x + 3 for x in arr],
lower: [x - 3 for x in arr],
evens: [x for x in arr if x % 2 == 0],
odds: [x for x in arr if x % 2 == 1],
evens_and_odds: [
'%d-%d' % [x, y]
for x in arr
if x % 2 == 0
for y in arr
if y % 2 == 1
],
},
object_comprehensions: {
evens: {
['f' + x]: true
for x in arr
if x % 2 == 0
},
// Use object composition (+) to add in
// static fields:
mixture: {
f: 1,
g: 2,
} + {
[x]: 0
for x in ['a', 'b', 'c']
},
},
}
执行
jsonnet demo.jsonnet > demo.json
输出
{
"cocktails": {
"Bee's Knees": {
"garnish": "Lemon Twist",
"ingredients": [
{
"kind": "Honey Syrup",
"qty": 1.3333333333333333
},
{
"kind": "Lemon Juice",
"qty": 1.3333333333333333
},
{
"kind": "Farmers Gin",
"qty": 1.3333333333333333
}
],
"served": "Straight Up"
},
"Screwdriver": {
"ingredients": [
{
"kind": "Vodka",
"qty": 1.5
},
{
"kind": "Orange Juice",
"qty": 3
}
],
"served": "On The Rocks"
},
"Yellow Screwdriver": {
"ingredients": [
{
"kind": "Vodka",
"qty": 1.5
},
{
"kind": "Lemonade",
"qty": 3
}
],
"served": "On The Rocks"
}
}
}
导入
编写 demo1.libsonnet,内容如下
local data = 1;
{
data: data,
}
编写 demo2.jsonnet,内容如下
local demo1 = import 'demo1.libsonnet';
{
data: demo1.data + 2,
}
执行
jsonnet demo2.jsonnet > demo2.json
输出
{
"data": 3
}
错误
编写 demo.jsonnet,内容如下
// Extend above example to sanity check input.
local equal_parts(size, ingredients) =
local qty = size / std.length(ingredients);
// Check a pre-condition
if std.length(ingredients) == 0 then
error 'Empty ingredients.'
else [
{ kind: i, qty: qty }
for i in ingredients
];
local subtract(a, b) =
assert a > b : 'a must be bigger than b';
a - b;
assert std.isFunction(subtract);
{
test1: equal_parts(1, ['Whiskey']),
test2: subtract(10, 3),
object: {
assert self.f < self.g : 'wat',
f: 1,
g: 2,
},
assert std.isObject(self.object),
}
执行
jsonnet demo2.jsonnet > demo2.json
输出
{
"object": {
"f": 1,
"g": 2
},
"test1": [
{
"kind": "Whiskey",
"qty": 1
}
],
"test2": 7
}
外部变量
编写 demo.jsonnet,内容如下
{
[std.extVar('prefix') + 'Pina Colada']: {
ingredients: [
{ kind: 'Rum', qty: 3 },
{ kind: 'Pineapple Juice', qty: 6 },
{ kind: 'Coconut Cream', qty: 2 },
{ kind: 'Ice', qty: 12 },
],
garnish: 'Pineapple slice',
served: 'Frozen',
},
[if std.extVar('brunch') then
std.extVar('prefix') + 'Bloody Mary'
]: {
ingredients: [
{ kind: 'Vodka', qty: 1.5 },
{ kind: 'Tomato Juice', qty: 3 },
{ kind: 'Lemon Juice', qty: 1.5 },
{ kind: 'Worcestershire', qty: 0.25 },
{ kind: 'Tobasco Sauce', qty: 0.15 },
],
garnish: 'Celery salt & pepper',
served: 'Tall',
},
}
执行
jsonnet demo2.jsonnet > demo2.json
输出
{
"Happy Hour Bloody Mary": {
"garnish": "Celery salt & pepper",
"ingredients": [
{
"kind": "Vodka",
"qty": 1.5
},
{
"kind": "Tomato Juice",
"qty": 3
},
{
"kind": "Lemon Juice",
"qty": 1.5
},
{
"kind": "Worcestershire",
"qty": 0.25
},
{
"kind": "Tobasco Sauce",
"qty": 0.14999999999999999
}
],
"served": "Tall"
},
"Happy Hour Pina Colada": {
"garnish": "Pineapple slice",
"ingredients": [
{
"kind": "Rum",
"qty": 3
},
{
"kind": "Pineapple Juice",
"qty": 6
},
{
"kind": "Coconut Cream",
"qty": 2
},
{
"kind": "Ice",
"qty": 12
}
],
"served": "Frozen"
}
}
面向对象
编写 demo.jsonnet,内容如下
local Base = {
f: 2,
g: self.f + 100,
};
local WrapperBase = {
Base: Base,
};
{
Derived: Base + {
f: 5,
old_f: super.f,
old_g: super.g,
},
WrapperDerived: WrapperBase + {
Base+: { f: 5 },
},
}
执行
jsonnet demo2.jsonnet > demo2.json
输出
{
"Derived": {
"f": 5,
"g": 105,
"old_f": 2,
"old_g": 105
},
"WrapperDerived": {
"Base": {
"f": 5,
"g": 105
}
}
}
