Rails 我一直觉得 Sunspot#search 的 DSL 很酷，但是以我现在的能力实在是看不懂怎么实现，有没有高人来研究一下
MyClass.solr_search do
any_of do
with :col1, 1
with :col2, 2
all_of do
with :col3, 3
without :col4, 4
end
end
end
像这样，all_of和any_off可以无限层嵌套，分别代表or和and, with代表等于， without代表！等于，在这样的 DSL 里面结合业务逻辑就很清晰，但是现在要使用 ElastivSearch 了，那个封装的就比较浅，没有这样的 DSL 可以用了，我想把这套思路搬出来，于是去看了源码，最深处看到两行有点懵
class ContextBoundDelegate
class <<self
def instance_eval_with_context(receiver, &block)
calling_context = eval('self', block.binding)
if parent_calling_context = calling_context.instance_eval{@__calling_context__ if defined?(@__calling_context__)}
calling_context = parent_calling_context
end
...
eval('self', block.binding)
这个什么意思呢， 顺便问一下 block 里面无限嵌套 block 的思路怎么实现
这种风格的核心原理是 obj.instance_exec(&block) 你 google 搜 Ruby DSL 就能看到很多风格 DSL 是怎么做的了
跟 rails 的 route 差不多，试着撸一个简陋的：
module Search
def self.ing &blk
Root.new.tap do |r|
r.instance_eval(&blk)
puts r
end
end
def children
@chidlren ||= []
end
def with condition, value
children << With.new(condition, value)
end
def without condition, value
children << Without.new(condition, value)
end
def any_of &blk
a = Any.new
a.instance_eval &blk
children << a
end
def all_of &blk
a = All.new
a.instance_eval &blk
children << a
end
def children_to_s
children.map &:to_s
end
class Root
include Search
def to_s
children.first.to_s
end
end
class Any
include Search
def to_s
'(' + children_to_s.join(' or ') + ')'
end
end
class All
include Search
def to_s
'(' + children_to_s.join(' and ') + ')'
end
end
class With
def initialize cond, v
@cond, @v = cond, v
end
def to_s
"#{@cond} = #{@v}"
end
end
class Without
def initialize cond, v
@cond, @v = cond, v
end
def to_s
"#{@cond} != #{@v}"
end
end
end
Search.ing do
any_of do
with :col1, 1
with :col2, 2
all_of do
with :col3, 3
without :col4, 4
end
end
end
# output
# (col1 = 1 or col2 = 2 or (col3 = 3 and col4 != 4))
我临时写了一个比较符合 ES 的
class MyDsl
def initialize
@hash = {}
end
def method_missing method_name, k=nil, v=nil, &block
if block_given?
new_container = self.class.new
new_container.instance_eval(&block)
@hash[method_name] = new_container.to_h
else
@hash[method_name] ||= {}
@hash[method_name][k] = v
end
end
def to_h
@hash
end
end
es = MyDsl.new
es.bool do
must do
match 'title', 'test'
end
end
es.to_h
=> {:bool=>{:must=>{:match=>{"title"=>"test"}}}}