Try.cr

1.value-and-exception.cr

def parse(str)
  JSON.parse(str)
end

pp parse("1") # => 1
pp parse("x") # raise JSON::ParseException

begin
  v = parse("1")
  # use v
rescue
  # ...
end

# Not useful

2.value-and-nil.cr

def parse(str)
  JSON.parse(str)
rescue
  nil
end

pp parse("1") # => 1
pp parse("x") # => nil

# Useful, but what happened?

3.wrap-value-with-try.cr

def parse(str)
  Try(JSON::Any).try {
    JSON.parse(str)
  }
end

pp parse("1") # => #<Success(JSON::Any):0x2257d00 @value=1>
pp parse("x") # => #<Failure(JSON::Any):0x2257960 @value=...

v = parse("1")
case v
when Success
  v.get  # => JSON::Any
when Failure
  v.failed.value  # => JSON::ParseException
end

# We can see what happened, but useful?

# Yup, it's useful because we can chain it!

def to_int(v)
  Try(Int32).try { v.to_s.to_i }
end

def pretty_size(v)
  Try(String).try { "%.1f KB" % [v / 1000.0] }
end

p parse("1").flat_map{|v| to_int(v)}.flat_map{|v| pretty_size(v)} # => #<Success(String):0x18feee0 @value="0.0 KB">
p parse("x").flat_map{|v| to_int(v)}.flat_map{|v| pretty_size(v)} # => #<Failure(String):0x17b1ae0

x.scala-has-first-class-method.md

crystal

parse("1").flat_map{|v| to_int(v)}.flat_map{|v| pretty_size(v)}
parse("x").flat_map{|v| to_int(v)}.flat_map{|v| pretty_size(v)}

scala

parse("1").flatMap(to_int).flatMap(pretty_size)
parse("x").flatMap(to_int).flatMap(pretty_size)

Readable code! Beautiful! Because methods are first class objects.