indent=(string)[permalink][rdoc]インデントに使用する文字列をセットします。
例
require "json"
json_state = JSON::State.new(indent: "\t")
json_state.indent # => "\t"
JSON.generate({key1: "value1", key2: "value2"}, json_state)
# => "{\t\"key1\":\"value1\",\t\"key2\":\"value2\"}"
json_state.indent = "  "
JSON.generate({key1: "value1", key2: "value2"}, json_state)
# => "{  \"key1\":\"value1\",  \"key2\":\"value2\"}"