Add Hash#last_key and Hash#last_value (#5760)

j8r · RX14 · commit 3138b520651c · 2018-04-07T21:25:03.000+01:00
diff --git a/spec/std/hash_spec.cr b/spec/std/hash_spec.cr
@@ -482,6 +482,16 @@ describe "Hash" do
     h.first_value.should eq(2)
   end
 
+  it "gets last key" do
+    h = {1 => 2, 3 => 4}
+    h.last_key.should eq(3)
+  end
+
+  it "gets last value" do
+    h = {1 => 2, 3 => 4}
+    h.last_value.should eq(4)
+  end
+
   it "shifts" do
     h = {1 => 2, 3 => 4}
     h.shift.should eq({1, 2})
diff --git a/src/hash.cr b/src/hash.cr
@@ -612,8 +612,8 @@ class Hash(K, V)
   # Returns the first key if it exists, or returns `nil`.
   #
   # ```
-  # hash = {"foo" => "bar"}
-  # hash.first_key? # => "foo"
+  # hash = {"foo1" => "bar1", "foz2" => "baz2"}
+  # hash.first_key? # => "foo1"
   # hash.clear
   # hash.first_key? # => nil
   # ```
@@ -626,11 +626,52 @@ class Hash(K, V)
     @first.not_nil!.value
   end
 
-  # Similar to `#first_key?`, but returns its value.
+  # Returns the first value if it exists, or returns `nil`.
+  #
+  # ```
+  # hash = {"foo1" => "bar1", "foz2" => "baz2"}
+  # hash.first_value? # => "bar1"
+  # hash.clear
+  # hash.first_value? # => nil
+  # ```
   def first_value?
     @first.try &.value
   end
 
+  # Returns the last key in the hash.
+  def last_key
+    @last.not_nil!.key
+  end
+
+  # Returns the last key if it exists, or returns `nil`.
+  #
+  # ```
+  # hash = {"foo1" => "bar1", "foz2" => "baz2"}
+  # hash.last_key? # => "foz2"
+  # hash.clear
+  # hash.last_key? # => nil
+  # ```
+  def last_key?
+    @last.try &.key
+  end
+
+  # Returns the last value in the hash.
+  def last_value
+    @last.not_nil!.value
+  end
+
+  # Returns the last value if it exists, or returns `nil`.
+  #
+  # ```
+  # hash = {"foo1" => "bar1", "foz2" => "baz2"}
+  # hash.last_value? # => "baz2"
+  # hash.clear
+  # hash.last_value? # => nil
+  # ```
+  def last_value?
+    @last.try &.value
+  end
+
   # Deletes and returns the first key-value pair in the hash,
   # or raises `IndexError` if the hash is empty.
   #
