I have Ruby code that looks vaguely like this.
str = 2010-12-02_12-10-26
puts str
puts DateTime.parse(str, "%Y-%m-%d_%H-%M-%S")
I expected to get the actual time from the parse. Instead, I'm getting output like this...
2010-12-02_12-10-26
2010-12-02T00:00:00+00:00
How do I get the time parsed in as well?
This works:
str = "2010-12-02_12-10-26"
puts str
puts DateTime.strptime(str, "%Y-%m-%d_%H-%M-%S")
This example on Codepad.
According to the documentation parse:
Create a new DateTime object by parsing from a String, without specifying the format.
And strptime:
Create a new DateTime object by parsing from a String according to a specified format.
Use strptime instead of parse
puts DateTime.strptime(str, "%Y-%m-%d_%H-%M-%S")
Related
I need to format a string to date:
date = DateTime.parse("05/15/2017")
formatted_date = date.strftime('%m/%d/%Y')
puts formatted_date
But I'm getting an error:
`parse': invalid date (ArgumentError)
And if I try to parse 15/05/2017 then it works.
How to parse 05/15/2017 into %m/%d/%Y format?
It is the first line that raises the error, because Date.parse doesn't know how to handle the string "05/15/2016". Use Date.strptime instead and tell Ruby how to read the string:
DateTime.strptime('05/15/2017', '%m/%d/%Y')
#=> #<DateTime: 2017-05-15T00:00:00+00:00 ((2457889j,0s,0n),+0s,2299161j)>
I have some data I was writing from one CSV to another CSV because I need to do some data manipulation.
I noticed the CSV library has some default converters that are taking my values that look like dates and parsing those into new date strings.
I was wondering if I could remove all converters? I tried using my custom converter, but no matter what I do it seems that the dates keep getting parsed.
Here is my code simplified:
require 'csv'
CSV::Converters[:my_converter] = lambda do |value|
value
end
CSV.open('new-data.csv', 'w') do |csv|
data = CSV.read('original-data.csv', :converters => [:my_converter]).each do |row|
csv << row
end
end
The value 9/30/14 0:00 is getting changed to 9/30/2014 0:00, for example.
Are you sure that your CSV file doesn't actually contain the 4-digit year? Try looking at puts File.read('original-data.csv')
When I tried this on Ruby 2.1.8, it didn't change the value
require 'csv'
my_csv_data = 'hello,"9/30/14 0:00",world'
CSV.new(my_csv_data).each do |row|
puts row.inspect # prints ["hello", "9/30/14 0:00", "world"], as expected
end
CSV files are not parsed and converted into objects, the data in the fields is returned as a string. Always. This behavior is different than YAML or JSON, which do convert back to their base types.
Consider this:
require 'csv'
CSV.parse("1,10/1/14,foo") # => [["1", "10/1/14", "foo"]]
All values are strings.
csv = ["foo", 'bar', 1, Date.new(2014, 10, 1)].to_csv # => "foo,bar,1,2014-10-01\n"
Converting an array containing native Ruby objects results in a string of comma-delimited values.
CSV.parse(csv) # => [["foo", "bar", "1", "2014-10-01"]]
Reparsing that string returns the string versions but doesn't attempt to return them to their original types as CSV doesn't have a way of knowing what those were. The developer (you) has to know and do that.
The end-result of all that is that CSV won't change a year from '14' to '2014'. It doesn't know that it's a date, and, because it's not CSV's place to convert to objects, it only splits the fields appropriately and passes the information on to be massaged by the developer.
I have a JSON string which has been generated by Jbuilder:
json = "{name: 'Peter', email: 'peter#stackoverflow.com'}"
This is currently a string. However I want to combine it into a new hash (ideally in Ruby) before finally outputting it as JSON.
i.e.
output = {result: :success, data: json}
However if I convert this to JSON the json value gets double-encoded such that it's sent as a string:
output.to_json
#=> "{\"result\":\"success\",\"data\":\"{name: 'Peter', email: 'peter#stackoverflow.com'}\"}"
Now I could parse the JSON into a Ruby hash and then re-output it but that seems like a big fat waste of parsing when what I'd really like to do is to say "hey, this node is already JSON, don't re-encode it already!".
Is there any equivalent to the raw() method Rails has in views? i.e.
output = {result: :success, data: raw(json)}
so that the json evaluation of this then becomes:
output.to_json
#=> "{\"result\":\"success\",\"data\": {\"name\":\"Peter\",\"email\":\"peter#stackoverflow.com\"}"
Here’s a way you can do this, it’s a bit of a hack but you might find it useful.
First restating the problem:
# Note the quotes, your example isn't actually valid
json = "{\"name\": \"Peter\", \"email\": \"peter#stackoverflow.com\"}"
output = {result: :success, data: json}
# Without changing anything
puts JSON.generate(output)
This results in the following, where the value of data is a single string:
{"result":"success","data":"{\"name\": \"Peter\", \"email\": \"peter#stackoverflow.com\"}"}
The json gem uses a to_json method that is added to all objects to convert them to json, so the simplest fix would be to replace that method on objects you want to behave differently:
# As before
json = "{\"name\": \"Peter\", \"email\": \"peter#stackoverflow.com\"}"
# Replace to_json on the singleton object
def json.to_json *args
self
end
output = {result: :success, data: json}
# Generate the output (output.to_json gives the same result)
puts JSON.generate(output)
This creates the following, where the data value is now itself a hash, as desired:
{"result":"success","data":{"name": "Peter", "email": "peter#stackoverflow.com"}}
A cleaner way to do this, to avoid manipulating singletons in your code could be to create a subclass of string that has this behaviour:
class JsonSafeString < String
def to_json *args
self
end
end
You can now create a JsonSafeString when you want the contents included directly in a JSON object:
json = "{\"name\": \"Peter\", \"email\": \"peter#stackoverflow.com\"}"
output = {result: :success, data: JsonSafeString.new(json)}
puts JSON.generate(output)
The result is the same as above:
{"result":"success","data":{"name": "Peter", "email": "peter#stackoverflow.com"}}
You could wrap the call to JsonSafeString.new in a method like raw_json if you wanted.
Obviously this leaves the task of ensuring your string is valid to you – the main point of using a library for this is the user doesn’t have to concern themselves with things like whether to use single or double quotes, so you could be vulnerable to generating invalid JSON if you’re not careful. Also this is just a quick hack, there are probably a load of things I haven’t considered. In particular I haven’t taken character encodings into account, so watch out.
This doesn't address your question, but may help you avoid it altogether...
Do you really need to generate your json variable into JSON before adding it to the hash? Jbuilder can generate a hash just as easily as a JSON string, e.g.:
hash = Jbuilder.new do |json|
json.name 'Peter'
json.email 'peter#stackoverflow.com'
end.attributes!
# => {"name"=>"Peter", "email"=>"peter#stackoverflow.com"}
output = {result: :success, data: hash}
eval will put it out as raw code.
eval "{name: 'Peter', email: 'peter#stackoverflow.com'}"
=> {:name=>"Peter", :email=>"peter#stackoverflow.com"}
And the results.
output = {result: :success, data: eval("{name: 'Peter', email: 'peter#stackoverflow.com'}") }
=> {:result=>:success, :data=>{:name=>"Peter", :email=>"peter#stackoverflow.com"}}
And to string
output.to_s
=> "{:result=>:success, :data=>{:name=>\"Peter\", :email=>\"peter#stackoverflow.com\"}}"
And JSON
require 'json'
=> true
output.to_json
=> "{\"result\":\"success\",\"data\":{\"name\":\"Peter\",\"email\":\"peter#stackoverflow.com\"}}"
I'd like to be able to change the date and time formats used by CSV when generating csv output. For example, instead of generating '2004-1-30' for a date, I'd like it to generate '1/30/2004'.
How can I do that?
Here is a complete example :
require 'csv'
require 'date'
str = <<_
2004-1-30,foo
2004-11-20,bar
_
File.write('a',str)
CSV::Converters[:cdate] = lambda do |s|
begin
Date.strptime(s,"%Y-%m-%d").strftime("%-m/%d/%Y")
rescue ArgumentError
s
end
end
CSV.foreach('a',:converters => :cdate) do |row|
p row
end
# >> ["1/30/2004", "foo"]
# >> ["11/20/2004", "bar"]
Look at the documentation of Converters.
An Array of names from the Converters Hash and/or lambdas that handle custom conversion. A single converter doesn’t have to be in an Array. All built-in converters try to transcode fields to UTF-8 before converting. The conversion will fail if the data cannot be transcoded, leaving the field unchanged.
I'm looking for the best way to take a datetime string from MySQL, explode it in Ruby and return the month, date, and year in separate elements.
How is the string formatted? You could just convert the datetime string into a datetime object, and call the instance methods.
require 'time'
x = "2009/04/16 19:52:30" #grab your datetime string from the database and assign it
y = DateTime.strptime(x, "%Y/%m/%d %H:%M:%S") #create a new date object
Then a simple y.day() yields:
y.day() = 16
and y.hour():
y.hour() = 19
FYI never actually used Ruby much, so this is what I got out of playing with the console, so hopefully this helps shed some light.
require 'time'
x = "2009/04/16 19:52:30"
begin
y = Time.parse(x)
[y.year, y.month, y.day] # => [2009, 4, 16]
rescue ArgumentError
puts "cannot parse date: #{x}"
end