Below I have an example active record query using a bunch of each iterators
user.user_spells.each do |us|
us.spell.buff_effects.where(stat_effected:'gold').each do |be|
value = value + be.value
end
end
I would like to use .map to return a list of all the results so I can do it essentially in one line.
I came up with:
user.user_spells.map { |us| us.spell.buff_effects.where(stat_effected:stat_effected) }.each do |be|
value = value + be.value
end
However... the .map block returns some empty arrays. Not sure how to write it correctly.
Any help would be appreciated! Thanks
Probably along these lines, if what you want is the sum of values in the end:
value =
user.user_spells.flat_map do |us|
us.spell.buff_effects.where(stat_effected:'gold').map(&:value)
end.reduce(&:+)
Related
In an API processing a large number of attributes, the following pattern is frequent
if !article[:ingredients].nil?
clean_ingredients = article[:ingredients].tr('*$+!##Â', ' ')
ingredients = clean_ingredients.downcase.capitalize
else
ingredients = nil
end
for a JSON string as: { "id": "YYYYYY", "article": [ { "ingredients": "long string", [...]
Unfortunately, a method defined as
def empty_and_clean(array_element, element_attribute)
if !array_element[:element_attribute].nil?
clean_ingredients = array_element[:element_attribute].tr('*$+!##Â', ' ')
ingredients = clean_ingredients.downcase.capitalize
else
ingredients = nil
end
end
cannot be called in the method as empty_and_clean(article, ingredients) as it returns
undefined local variable or method 'ingredients'
What syntax allows to refactor this pattern?
You can call your empty_and_clean method this way:
empty_and_clean(article, :ingredients)
Just modify empty_and_clean to use element_attribute directly rather than the symbol :element_attribute.
I suggest you read more about symbols in Ruby to understand how this works.
Also, array_element is a misleading name because it is an array, not an element of an array. array would be slightly better, but is still too generic. Maybe objects or something else that describes what is actually in the array.
I have a array which is inside a hash. I want know the result of the student (pass/fail) using the following array. First I have to match them with particular standard and compare their marks with the hash pass and fails. And I want to get the key pass or fail based on their mark. How to achieve this using Ruby?
array = [
{
:standard =>1
:pass=>{:tamil=>30,:eng=>25,:math=>35},
:fail=>{:tamil=>10,:eng=>15,:maths=>20}
},
{
:standard =>2,
:pass=>{:tamil=>40,:eng=>35,:math=>45},
:fail=>{:tamil=>20,:eng=>25,:maths=>30}
}
]
#student is assumed to be defined
standard = array.select {|standard| standard[:standard] == #student.standard}
eng_pass = #student.eng_mark >= standard[:pass][:eng]
eng_fail = #student.eng_mark <= standard[:fail][:eng]
return [eng_pass, eng_fail, whatever_else_you_want]
So on and forth for various topics.
The syntax in reading values from this structure is something like:
array[0][:pass][:eng]
and accordingly you can do the comparison as usual in batch:
for i in 0..#students_array.length
num = # student's score
standard = # something like array[0][:pass][:eng]
if num > standard
# something like 'put "You passed!"'
end
end
I'm using Rails and learning ActiveRecord and I came across a vexing problem. Here's an array in my model:
#sea_countries = ['Singapore','Malaysia','Indonesia', 'Vietnam', 'Philippines', 'Thailand']
And here's my ActiveRecord object:
#sea_funding = StartupFunding.joins(:startup)
.where('startups.locations LIKE ?', '%Singapore%')
What I'm trying to do is to return a result where a string in the 'locations' column matches any element in the Array. I'm able to match the strings to each element of an Array (as above), but I'm not sure how to iterate over the whole Array such that the element is included as long as there's one match.
The intent is that an element with multiple locations 'Singapore,Malaysia' would be included within #sea_funding as well.
Well, don't ask me why 'locations' is set as a string. It's just the way the previous developer did it.
You use an IN clause in your .where filter:
#sea_funding = StartupFunding.joins(:startup)
.where(["startups.locations IN (?)", #sea_countries])
#sea_countries.include?(startups.locations)
This will return a boolean TRUE if the value of the locations column in startups can be found in the sea_countries array, false if it is absent.
Could this work for you?
first = true
where_clause = nil
sea_countries.each do |country|
quoted_country = ActiveRecord::Base.connection.quote_string(country)
if first
where_clause = "startups.locations LIKE '%#{quoted_country}%' "
first = false
else
where_clause += "OR startups.locations LIKE '%#{quoted_country}%' "
end
end
#sea_funding = StartupFunding.joins(:startup)
.where(where_clause)
I implemented a function to group anagrams.
In a nutshell:
input: ['cars', 'for', 'potatoes', 'racs', 'four','scar', 'creams', scream']
output: [["cars", "racs", "scar"], ["four"], ["for"], ["potatoes"],["creams", "scream"]]
I would like to know if there is a better way to do this.
I really think I used too much repetition statements: until, select,
delete_if.
Is there any way to combine the select and delete_if statement? That
means, can selected items be automatically deleted?
Code:
def group_anagrams(words)
array = []
until words.empty?
word = words.first
array.push( words.select { |match| word.downcase.chars.sort.join.eql?(match.downcase.chars.sort.join ) } )
words.delete_if { |match| word.downcase.chars.sort.join.eql?(match.downcase.chars.sort.join ) }
end
array
end
Thanks in advance,
Like that:
a = ['cars', 'for', 'potatoes', 'racs', 'four','scar', 'creams', 'scream']
a.group_by { |element| element.downcase.chars.sort }.values
Output is:
[["cars", "racs", "scar"], ["for"], ["potatoes"], ["four"], ["creams", "scream"]]
If you want to you can turn this one-liner to a method of course.
You could use the partition function instead of select, implemented in Enumerable. It splits the entries within the array according to the decision-function into two arrays.
def group_anagrams(words)
array = []
until words.empty?
word = words.first
delta, words = words.partition { |match| word.downcase.chars.sort.join.eql?(match.downcase.chars.sort.join ) } )
array += delta
end
array
end
(untested)
I need help with this...
I have a hash like this:
#ingredients = Hash.new
#ingredients[1] = "Biscottes Mini(recondo)"
#ingredients[2] = "Abadejo"
#ingredients[3] = "Acelga"
#ingredients[4] = "Agua de Coco"
#ingredients[5] = "Ajo"
#ingredients[6] = "Almidón de Arroz"
#ingredients[7] = "Anillos Con Avena Integral cheerios (nestle)"
#ingredients[8] = "Apio"
I need to search into that hash in order to find "Biscottes Mini(recondo)" when I write "scotte"
Some help?
Thk!
Why do you use a Hash here and not an Array? You do not seem to use other keys than integers.
Anyway, this solution works for both Array and Hashes:
search_term = 'scotte'
# you could also use find_all instead of select
search_results = #ingredients.select { |key, val| val.include?(search_term) }
puts search_results.inspect
See http://ruby-doc.org/core/classes/Enumerable.html#M001488
You can call select (or find if you only want the first match) on a hash and then pass in a block that evaluates whether to include the key/value in the result hash. The block passes the key and value as arguments, so you can evaluate whether either the key or value matches.
search_value = "scotte"
#ingredients.select { |key, value| value.include? search_value }