Class: JsonTools::Pointer

Inherits:
Object
  • Object
show all
Defined in:
lib/jsontools/jsontools.rb

Defined Under Namespace

Classes: PointerError

Instance Method Summary collapse

Constructor Details

#initialize(path) ⇒ Pointer

Returns a new instance of Pointer.



51
52
53
54
55
56
 
# File 'lib/jsontools/jsontools.rb', line 51

def initialize path
  @parts = path.split('/').drop(1).map { |p|
      p.gsub(/\~1/, '/').gsub(/\~0/, '~') 
    }
  @last = @parts.pop
end

Instance Method Details

#exists?(context) ⇒ Boolean

True if the referenced path exists

Returns:

  • (Boolean) 


118
119
120
121
122
123
124
125
126
127
 
# File 'lib/jsontools/jsontools.rb', line 118

def exists? context
  p = parent context
  if Array === p
    (0...p.length).cover? Integer(@last)
  else
    p.has_key? @last
  end
rescue
  false
end

#last ⇒ Object

Returns the last segment of the JSON Pointer



59
 
# File 'lib/jsontools/jsontools.rb', line 59

def last; @last; end

#parent(context) ⇒ Object Also known as: []

Evaluates the pointer against the given context hash object and returns the parent. That is, if the Pointer is “/a/b/c”, parent will return the object referenced by “/a/b”, or nil if that object does not exist.



67
68
69
70
71
72
73
 
# File 'lib/jsontools/jsontools.rb', line 67

def parent context
  @parts.reduce(context) do |o, p| 
    o[(o.is_a?(Array) ? p.to_i : p)] 
  end
rescue
  raise PointerError
end

#value(context) ⇒ Object

Returns the specific value identified by this pointer, if any. Nil is returned if the path does not exist. Note that this does not differentiate between explicitly null values or missing paths.



102
103
104
105
 
# File 'lib/jsontools/jsontools.rb', line 102

def value context
  parent = parent context
  parent[JsonTools.fix_key(parent,@last)] unless !parent
end

#value_with_fail(context) ⇒ Object

Alternative to value that raises a PointerError if the referenced path does not exist.



109
110
111
112
113
114
115
 
# File 'lib/jsontools/jsontools.rb', line 109

def value_with_fail context
  parent = parent context
  fail if !parent
  parent.fetch(JsonTools.fix_key(parent,@last))
rescue
  raise PointerError
end

#walk(context) {|key, (!p ? nil : p[key])| ... } ⇒ Object

Enumerates down the pointer path, yielding to the given block each name, value pair specified in the path, halting at the first nil value encountered. The required block will be passed two parameters. The first is the accessor name, the second is the value. For instance, given the hash ‘a’=>{‘b’=>{‘c’=>123}}, and the pointer “/a/b/c”, the block will be called three times, first with [‘a’,‘b’=>{‘c’=>123}], next with [‘b’,‘c’=>123], and finally with [‘c’,123].

Yields:

  • (key, (!p ? nil : p[key])) 


87
88
89
90
91
92
93
94
95
96
 
# File 'lib/jsontools/jsontools.rb', line 87

def walk context
  p = @parts.reduce(context) do |o,p|
    n = o[(o.is_a?(Array) ? p.to_i : p)]
    yield p, n
    return if NilClass === n # exit the loop if the object is nil
    n
  end
  key = JsonTools.fix_key(p,@last)
  yield key, (!p ? nil : p[key])
end