I'm having trouble with a little Ruby on Rails I'm building and need some help.
I have a Table with 20+ Columns and a corresponding XML File which can be parsed as some sort of hash with a gem. Every key would be mapped to a column and every value would be a data record in said column.
The way I access a specific value in the already parsed XML file is:
filename["crs","inputkeyhere"]
which returns the value, for example "52" or whatever.
What I am trying to do is upload the file, parse it with the gem and give each column the corresponding value.
My table (or model) is called "Attributeset" and I already know how I can access every column:
#attributeset = Attributeset.new
#attributeset.attributes.keys
So my thought process was:
Iterate over all the keys
Pass every key into a block called |a|
Use the rails possibilty to set attributes by calling the corresponding #attributeset.
Set colum attribute to the corresponding xml key
So my code would go something like this:
#attributeset.attributes.keys.each do |a|
#attributeset.a=filename["crs",a]
end
But my problem is, that ruby thinks ".a" is a method and apparently does not evaluate "a" to the block parameter.
I've read through lambdas and procs and whatnot but didn't really understand how they could work for my specific situation.
Coming from bash scripting maybe my thinking might be wrong but I thought that the .a might get evaluated.
I know I can run the block with yield, but this only works in methods as far as I know..
Any help is appreciated.
Thanks and stay healthy,
Alex
Thanks for the input!
I wanted to make it as clean as possible, and not using any temporary hashes to pass arguments.
I've found the method
write_attribute
which can be used like this:
#attributeset.write_attribute(a, xmp["crs",a])
worked perfectly for me.
You can use []= method to set values dynamically:
#attributeset.attribute_names.each do |attribute|
#attributeset[attribute] = filename["crs", attribute]
end
Related
I'm currently trying to understand how permitted parameters works in ruby.
Usually, in my_model.rb I have:
has_many: some_other_model
*
*
*
def my_model_params
params.require(:my_model).permit( :column1, some_other_model_attributes %i[other_column1])
etc...
and in the update function
my_object.update_attributes(my_model_params)
with a well formatted json which has some my_model root, and some_other_model_attributes as a child (array) with values.
My problem is I receive a json like this one
However the different arrays inside (such as codification, general_information) do contain attributes of the mission (general_information contains reference that is a column in the mission table) but there isn't any column named codification, or relation to a codification_attributes.
So, when I add :
general_information: %i[reference] in the permitted params, it says unknown attribute 'general_information' for Mission.
If not, no error are raised but in the log I can see unpermitted_parameter: general_information. And my object is not updated.
Finally if I reject it, there is no more unpermitted_parameter: general_information in the log but my object is not updated either.
I tried to set config.action_controller.action_on_unpermitted_parameters to false in my development config, it did nothing and it's probably a bad idea for production environment anyway.
The use of .permit! (even if it works) is currently not an option. And even though I think the json needs to be re-formatted it'd be better to find an other solution.
Thanks for the help.
unpermitted_parameter: ... in logs in not a problem which you need to fix, it's just an info.
How it works - you just permit needed parameters, you may think about them as a hash. Unpermitted parameters will not go into the model even if they are present in params. It means when you call
my_object.update_attributes(my_model_params)
it works like
my_object.update_attributes(column1: value_for_column1_from_params)
Keys in params should be named exactly as columns in the model, otherwise you need to prepare params somehow before create/update
This is using Rails 4.2.0, Ruby 2.2.0.
What I'd like to do is use the data contained in a fixture object to verify that duplicates are caught before insertion into the same database:
test "identical entries should be impossible to create" do
dup_entry = Entry.new(entries(:test_entry))
assert_not dup_entry.save
end
(where Entry is a well-defined model with a controller method .new, and test_entry is a fixture containing some valid Entry instance.)
Unfortunately, this doesn't work because entries(:test_entry) is going to be an Entry, not a hash accepted by Entry.new.
I know that I can access fixture properties with an expression of the form fixture_objname.property in the associated tests, since whatever is specified in the YAML will automatically be inserted into the database and loaded. The problem with this is that I have to manually retype a bunch of property names for the object I just specified in the YAML, which seems silly.
The documentation also says I can get the actual model instances by adding self.use_instantiated_fixtures = true to the test class. However, there don't seem to be any instance_methods that will dump out the fixture's model instance (test_entry) in a hash format to feed back into the .new method.
Is there an idiomatic way to get what I want, or a different, easier way?
I believe you're looking for something like:
entries(:test_entry).attributes
entries(:test_entry).attributes.class # => Hash
You can also remove properties if needed:
entries(:admin).attributes.except("id")
Hope this helps.
I am aiming to serialise a set of objects into a file so as to create a backup. I have the start of that working, using a methods on the models (simplified here, assuming I have two ActiveRecords foo and bar):
def backup(file, foo, bar)
file.write(foo.to_json(root: true))
file.write(bar.to_json(root: true))
end
This gives me a file as I desire, in this case with two records:
{"foo":{"Account_id":1,"Name":"F","created_at":"2013-04-16T10:06:19Z","id":1,"updated_at":"2013-04-20T11:36:23Z"}}
{"bar":{"Account_id":1,"Name":"B","created_at":"2013-04-16T10:06:19Z","id":1,"updated_at":"2013-04-20T11:36:23Z"}}
At a later date I then want to read that backup in and reinstantiate those objects, probably then persisting them back to the database. My aim is to iterate through the file checking the type of each object, then instantiating the right object.
I have part of the logic, but not yet all of it, I haven't worked out how I determine the type of each serialised object before I instantiate it. The code I have for a restore is as follows:
def restore(file)
file.each_line do |line|
**<some magic that parses my line into objectType and objectHash>**
case objectType
when :foo
Foo.new.from_json(objectHash)
Foo.process
Foo.save!
when :bar
Bar.new.from_json(objectHash)
Bar.process
Bar.save!
end
end
end
What I'm looking for is the bit that goes in the "some magic" section. I can just write the code to parse the line directly to determine whether it's a foo or a bar, but I feel like there's probably some tricky Rails/Ruby way to do this that is automatic. Unfortunately, in this case Google is not being my friend. All I can see are pages that are focused on json in the web requests, but not parsing json back in this way. Is there something I'm missing, or should I just write the code to split the string directly and read the object type?
If I do write the code to split the string directly, I would write something along the lines of:
objectType = line[/^{"(\w*)"=>(.*)}/, 1]
objectHash = line[/{"(\w*)"=>(.*)}/, 2]
This is pretty ugly and I'm sure there's a better way (which I'm still looking into), but I'm not sure that this is even the right approach v's there being something that automatically looks at a json representation and knows from the root value what object to instantiate.
Lastly, the actual instantiation using from_json isn't working either, it isn't populating any of the fields on my ActiveRecord. It gives me nil parameters, so I think the parse syntax isn't right.
So, that makes three questions:
Is there a way to determine which object it is that I'm just missing, that is much cleaner?
If there isn't and I need to use a regexp, is there a syntax to get both bits of the line parsed in a single go, rather than my two lines with the same regexp?
The from_json syntax appears unhappy. Is there a syntax I'm missing here? (no longer a question - the code above is fixed, I was using as_json when it should have been to_json, although the documentation is rather unclear on that....)
(Note: edits over time to clarify my question, and because I've now got a regexp that works (didn't before), but still not sure it's very elegant.)
Further information - one of the problems here, as I dig into it further, is that the as_json isn't actually giving me json - what I have in the file is a hash, not json at all. Further, the values for created_at and lastupdated_at in the hash aren't quoted - so basically that's what's causing the parse on the way back in to fail. I've worked out that I should use to_json instead of as_json, although the documentation suggests that as_json should work.
I'm not sure I fully understand you're methodology, but I think using JSON.parse() would help.
There's some good information here http://mike.bailey.net.au/2011/02/json-with-ruby-and-rails/
This would help you translate the raw object back to a hash.
OK, so I think I've got something that works. I'm not convinced at all that it's elegant, but it gives me the result. I'll spend some time later trying to make it cleaner.
The code looks like this:
file.each_line do |line|
objectType = line[/^{"(\w*)":(.*)}/, 1]
objectJSON = line[/{"(\w*)":(.*)}/, 2]
objectHash = JSON.parse(objectJSON)
case objectType
when 'foo'
restoredFoo = Foo.new(objectHash.except('id', 'created_at', 'updated_at'))
restoredFoo.created_at = objectHash['created_at']
restoredFoo.updated_at = objectHash['updated_at']
restoredFoo.save!
end
when 'bar'
restoredBar = Bar.new(objectHash.except('id', 'created_at', 'updated_at'))
restoredBar.created_at = objectHash['created_at']
restoredBar.updated_at = objectHash['updated_at']
restoredBar.save!
end
end
Items of note:
I feel like there should be a way to create the object that isn't a JSON.parse, but rather would make use of the from_json method on the model. I'm not sure what the from_json is good for if it doesn't do this!!
I'm having fun with mass_assignment. I don't really want to use :without_protection => true, although this would be an option. My concern is that I do want the created_at and updated_at to be restored as they were, but I want a new id. I'm going to be doing this for a number of entities in my application, I didn't really want to end up replicating the attributes_protected in the code - it seems not very DRY
I'm still pretty sure my reg exp can give me both objectType and objectJSON in one call
But having said all that, it works, which is a good step forwards.
I am working with some code I found online:
def person_path(options)
# This is where the path of the query is constructed.
path = "/people/" # For this section of the LinkedIn API
if id = options.delete(:id)
path += "id=#{id}"
elsif url = options.delete(:url)
path += "url=#{CGI.escape(url)}"
else
path += "~"
end
end
I am not completely certain what it does. what I am trying to do is have it construct a string something like this: http://api.linkedin.com/v1/people/~:(current-status) which I got from the LinkedIn developer docs here: https://developer.linkedin.com/documents/profile-api
Any thoughts on what I should pass this functions and how exactly it accomplishes what it does?
Thanks!
Whilst it's not stated what 'options' is, it's extremely common to pass in options to a method as a Hash of key-value pairs in Ruby, so I'd say that options is just that (with 99% certainty). This is the part that's key to understanding the rest of the code.
I believe that the #delete method on hash is being used in order to pull out the key-value pair and assign the value in one move, whilst taking advantage of the returned object's "truthiness".
http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-delete
And by "truthiness", I mean that in Ruby, all objects evaluate to 'true' except 'nil' and 'false'.
The rest is simple if-else control flow logic that you will have seen in any other language, so I hope this makes sense.
This just creates a path of the form "/people/id=foo" or "/people/url=foo_with_%_escapes" if it finds id or url in the options. As a side effect, it deletes the one it finds from the options. If it doesn't find either one, it gives "/people/~"
Yet another ruby question but this is a bunch of questions in one. I'm really starting to like rails but there are some questions that I'd just like to ask straight out.
Right now, I'm implementing a queue in sqlite. I already have a scaffold setup with this working OK. The purpose is for a web crawler to read through the array and determine which links he should crawl next.
The architecture in the program is 2 controllers. one for Job and one for crawler. The Jobs has the standard Crud interface supplied by scaffold. Where I'm falling down is I'm still trying to understand how these things communicate with eachother.
The Job is formatted as a url:string and depth:decimal. The table is already populated with about 4 objects.
#sitesToCrawl = Job.all
#sitesToCrawl.each {|x|puts Job.url}
I have a bunch of questions about the above.
At the moment, this was supposed to display all the jobs and I foolishly thought it would display plain text but its actually a hexidecimal pointer to the object itself. What Im trying to do is iterate through the #sitesToCrawl and put out each Jobs url.
Questions start here:
1: I know ruby is dynamically typed. Will #sitesToCrawl become an array like i want it to be with each slot containing a job.
2: #sitesToCrawl.each is pretty straighforward and I'm assuming its an iterator.
is X the name od the method or what is the purpose of the symbol or string between |*|
3: Puts and print are more or less the same yes? if i say #x = puts 3 then would x be 3?
4: Job.url. Can objects be referenced this way or should I be using
##sitesToCrawl = db.execute("SELECT url FROM jobs;")
where db is a new database
As Rubish Gupta pointed out, in your block, you should do x.url, otherwise you're trying to access the url method on the class Job, not on instances of Job. In other words, in blocks, the items in the pipes are the arguments of the block, and each will iterate through your array, passing in one item at a time to your block. Check out the doc here.
Just to extend this idea, each on Hashes (associative arrays, maps, whatever you know them as) will pass two variables to your block: a key and a value, like this:
a_hash.each {|key_var, val_var| puts "#{key_var} is associated with #{val_var}"}
Also, it's been a bit since I've done plain ActiveRecord models, but you might look into doing
#sitesToCrawl = Job.all.to_a
since Job.all is a lazy finder in that it's building a query in potentia: you've essentially built a query string saying SELECT * FROM jobs, but it might not be executed until you try to access the items. each might do that, I can't remember off the top of my head, but if you're using a debugger to look at it, I know you need to_a to get it to run the query.
You should absolutely be using job_instance.url - that's the beauty of ActiveRecord, it makes database access easy, provided everything gets set up right :)
Finally, puts and print are almost the same - the difference is that puts "string" is essentialy print "sting"; STDOUT.flush - it flushes at the end of the statement.