I'm new in ruby. I'm trying to do the following but haven't succeeded.
I've got an array of objects, let's call it objs. Each object has multiple properties, one of those is a variable that holds a number, let's call it val1. I wanna iterate through the array of objects and determine the max value of val1 through all the objects.
I've tried the following:
def init(objs)
#objs = objs
#max = 0
cal_max
end
def cal_max
#max = #objs.find { |obj| obj.val1 >= max }
# also tried
#objs.each { |obj| #max = obj.val1 if obj.val1 >= #max }
end
As I said, I'm just learning about blocks.
Any suggestion is welcome.
Thanks
Let's say you have set up the following model:
class SomeObject
attr_accessor :prop1, :prop2, :val1
def initialize(prop1, prop2, val1)
#prop1 = prop1
#prop2 = prop2
#val1 = val1
end
end
#define your objects from the class above
david = SomeObject.new('David', 'Peters', 23)
steven = SomeObject.new('Steven', 'Peters', 26)
john = SomeObject.new('John', 'Peters', 33)
#define an array of the above objects
array = [david, steven, john]
Then use max_by by passing the condition into its block as follows to determine the object with the max val1 value. Finally call val1 to get the value of the max object.
array.max_by {|e| e.val1 }.val1 #=> 33
You may also consider using hashes (negating the need to define a new class), like so:
david = {f_name: 'David', s_name: 'Peters', age: 23}
steven = {f_name: 'Steven', s_name: 'Peters', age: 26}
john = {f_name: 'John', s_name: 'Peters', age: 33}
array = [david, steven, john]
array.max_by { |hash| hash[:age] }[:age] #=> 33
#objs.map(&:val1).max
That will invoke the method on each object, and create a new array of the results, and then find the max value. This is shorthand for:
#objs.map{ |o| o.val1 }.max
Alternatively, you can select the object with the largest value, and then operate on it (as properly recomended by Cary Swoveland below):
#objs.max_by(&:val1).val1
Related
I have a class People with three properties
class People
attr_accessor :first_name, :last_name, :age
end
And I have two arrays:
a = [p1, p2]
b = [p3, p4]
Is there any easy way to combine these two arrays in a new array and remove the item with a condition like:
p1.first_name + p1.last_name == p3.first_name + p3.last_name
And after that all the item should be belong to array a
For example
p1.first_name = "Ada"
p1.last_name = "Wang"
p1.age = 28
p2.first_name = "Leon"
p2.last_name = "S"
p2.age = 28
p3.first_name = "Ada"
p3.last_name = "Wang"
p3.age = 18
p4.first_name = "Mario"
p4.last_name = "M"
p4.age = 80
the result should be [p1] the 28 years old Ada.Wang
I'm not sure I get your point, but maybe this is a possible option.
c = a + b
c.uniq! { |e| e.first_name && e.last_name }
Call Array#uniq! with a block on c which is the concatenation of a and b.
If arrays a and b themselves do not contain people with matching first and last names then this would work:
b.each_with_index do |p, i|
if !(b[i].first_name == a[i].first_name and b[i].last_name == a[i].last_name)
a.push(p) # as people p does not contain the same first/last names as a it can now be added to a
end
end
To check for other fields simply replace first_name / last_name with other variables.
I have to iterate through two arrays and calculate the salary total of the matching employee name.I have two arrays: empData:[Emp1,Emp2] and
salData:[[name:Emp1,sal:1000],[name:Emp2,sal:5000],[name:Emp1,sal:6000],[name:Emp1,sal:7000]].I have to loop through empData and also salData and calculating the sum of the salary for the matching emp name and then push both the user name and the corresponding sal in to an array.
double total
empData.each{x ->
sapData.each{ y ->
if(y.name == x)
{
total =total + y.sal;
}
}
But getting an error Cannot cast object 'null1000.0' with class'java.lang.String' to class 'java.lang.Double'. If i declare total as string then the result is the cancatenation of sal.
You are not initializing total to anything. It is also possible that your salary values are actually strings; hard to tell from what you provided.
Initialize total to 0, and make sure to cast y.sal to double if necessary.
Ugh, loops and loops... have a look at the Groovy collection methods.
// poor emp3 has no salaryData
def employeeNames = ['emp1', 'emp2', 'emp3']
def salaryData = [[name: 'emp1', sal: 1000], [name: 'emp2', sal: 5000], [name: 'emp1', sal: 6000], [name:'emp1', sal: 7000]]
// here's our output array variable
def output = []
// for each employee
// find all the salaryData elements where salaryData.name == employeeName
// using that list, collect just the salary value
// using that list, sum it, adding to an initial value of 0
// append a new entry in output containing the name, and total salary
employeeNames.each { employeeName ->
output << [name: employeeName, totalSalary: salaryData.findAll { sal -> sal.name == employeeName }.collect { sal -> sal.sal }.sum(0)]
}
println output
groovyconsole yields:
[[name:emp1, totalSalary:14000], [name:emp2, totalSalary:5000], [name:emp3, totalSalary:0]]
I start with an empty array, and a Hash of key, values.
I would like to iterate over the Hash and compare it against the empty array. If the value for each k,v pair doesn't already exist in the array, I would like to create an object with that value and then access an object method to append the key to an array inside the object.
This is my code
class Test
def initialize(name)
#name = name
#values = []
end
attr_accessor :name
def values=(value)
#values << value
end
def add(value)
#values.push(value)
end
end
l = []
n = {'server_1': 'cluster_x', 'server_2': 'cluster_y', 'server_3': 'cluster_z', 'server_4': 'cluster_x', 'server_5': 'cluster_y'}
n.each do |key, value|
l.any? do |a|
if a.name == value
a.add(key)
else
t = Test.new(value)
t.add(key)
l << t
end
end
end
p l
I would expect to see this:
[
#<Test:0x007ff8d10cd3a8 #name=:cluster_x, #values=["server_1, server_4"]>,
#<Test:0x007ff8d10cd2e0 #name=:cluster_y, #values=["server_2, server_5"]>,
#<Test:0x007ff8d10cd1f0 #name=:cluster_z, #values=["server_3"]>
]
Instead I just get an empty array.
I think that the condition if a.name == value is not being met and then the add method isn't being called.
#Cyzanfar gave me a clue as to what to look for, and I found the answer here
https://stackoverflow.com/a/34904864/5006720
n.each do |key, value|
found = l.detect {|e| e.name == value}
if found
found.add(key)
else
t = Test.new(value)
t.add(key)
l << t
end
end
#ARL you're almost there! The last thing you need to consider is when found actually returns an object since detect will find a matching one at some point.
n.each do |key, value|
found = l.detect {|e| e.name == value}
if found
found.add(key)
else
t = Test.new(value)
t.add(key)
l << t
end
end
You actually only want to add a new instance of Test when found return nil. This code should yield your desired output:
[
#<Test:0x007ff8d10cd3a8 #name=:cluster_x, #values=["server_1, server_4"]>,
#<Test:0x007ff8d10cd2e0 #name=:cluster_y, #values=["server_2, server_5"]>,
#<Test:0x007ff8d10cd1f0 #name=:cluster_z, #values=["server_3"]>
]
I observe two things in your code :
def values=(value)
#values << value
def add(value)
#values.push(value)
two methods do the same thing, pushing a value, as << is a kind of syntactic sugar meaning push
you have changed the meaning of values=, which is usually reserved for a setter method, equivalent to attire_writer :values.
Just to illustrate that there are many ways to do things in Ruby, I propose the following :
class Test
def initialize(name, value)
#name = name
#values = [value]
end
def add(value)
#values << value
end
end
h_cluster = {} # intermediate hash whose key is the cluster name
n = {'server_1': 'cluster_x', 'server_2': 'cluster_y', 'server_3': 'cluster_z',
'server_4': 'cluster_x', 'server_5': 'cluster_y'}
n.each do | server, cluster |
puts "server=#{server}, cluster=#{cluster}"
cluster_found = h_cluster[cluster] # does the key exist ? => nil or Test
# instance with servers list
puts "cluster_found=#{cluster_found.inspect}"
if cluster_found
then # add server to existing cluster
cluster_found.add(server)
else # create a new cluster
h_cluster[cluster] = Test.new(cluster, server)
end
end
p h_cluster.collect { | cluster, servers | servers }
Execution :
$ ruby -w t.rb
server=server_1, cluster=cluster_x
cluster_found=nil
server=server_2, cluster=cluster_y
cluster_found=nil
server=server_3, cluster=cluster_z
cluster_found=nil
server=server_4, cluster=cluster_x
cluster_found=#<Test:0x007fa7a619ae10 #name="cluster_x", #values=[:server_1]>
server=server_5, cluster=cluster_y
cluster_found=#<Test:0x007fa7a619ac58 #name="cluster_y", #values=[:server_2]>
[#<Test:0x007fa7a619ae10 #name="cluster_x", #values=[:server_1, :server_4]>,
#<Test:0x007fa7a619ac58 #name="cluster_y", #values=[:server_2, :server_5]>,
#<Test:0x007fa7a619aac8 #name="cluster_z", #values=[:server_3]>]
I am trying to access a specific value inside an array. The array contains specific class instance variables and is as follows:
[[#<Supermarket:0x007f8e989daef8 #id=1, #name="Easybuy">,
#<Delivery:0x007f8e989f98a8 #type=:standard, #price=5.0>],
[#<Supermarket:0x007f8e99039f88 #id=2, #name="Walmart">,
#<Delivery:0x007f8e989f98a8 #type=:standard, #price=5.0>],
[#<Supermarket:0x007f8e9901a390 #id=3, #name="Forragers">,
#<Delivery:0x007f8e989eae20 #type=:express, #price=10.0>]]
I want to iterate over each array inside the array and find out how many Delivery's within the array have #type:standard. Is this possible? Thank you in advance
array_of_array.inject(0) do |sum, array|
sum + array.count { |el| el.class == Delivery && el.instance_variable_get(:#type) == :standard }
end
You can use select() to filter the elements of an array.
Reconstructing your data:
require 'ostruct'
require 'pp'
supermarket_data = [
['Easybuy', 1],
['Walmart', 2],
['Forragers', 3],
]
supermarkets = supermarket_data.map do |(name, id)|
supermarket = OpenStruct.new
supermarket.name = name
supermarket.id = id
supermarket
end
delivery_data = [
['standard', 5.0],
['standard', 5.0],
['express', 10.0],
]
deliveries = delivery_data.map do |(type, price)|
delivery = OpenStruct.new
delivery.type = type
delivery.price = price
delivery
end
combined = supermarkets.zip deliveries
pp combined
[[#<OpenStruct name="Easybuy", id=1>,
#<OpenStruct type="standard", price=5.0>],
[#<OpenStruct name="Walmart", id=2>,
#<OpenStruct type="standard", price=5.0>],
[#<OpenStruct name="Forragers", id=3>,
#<OpenStruct type="express", price=10.0>]]
Filtering the array with select():
standard_deliveries = combined.select do |(supermarket, delivery)|
delivery.type == 'standard'
end
pp standard_deliveries # pretty print
p standard_deliveries.count
[[#<OpenStruct name="Easybuy", id=1>,
#<OpenStruct type="standard", price=5.0>],
[#<OpenStruct name="Walmart", id=2>,
#<OpenStruct type="standard", price=5.0>]]
2
I have a 2D array:
a = [["john doe", "01/03/2017", "01/04/2017", "event"], ["jane doe", "01/05/2017", "01/06/2017", "event"]...]
I would like to convert it to a value object in ruby. I found how to do it with a hash Ruby / Replace value in array of hash in the second answer of this question but not a 2D array. I would like to assign the value at a[0][0] to an attribute named "name", a[0][1] to "date1", a[0][2] to "date2" and a[0][3] to "event".
This is something like what I'd like to accomplish although it is not complete and I dont know how to assign multiple indexes to the different attributes in one loop:
class Schedule_info
arrt_accessor :name, :date1, :date2, :event
def initialize arr
#I would like this loop to contain all 4 attr assignments
arr.each {|i| instance_variable_set(:name, i[0])}
This should be short and clean enough, without unneeded metaprogramming :
data = [["john doe", "01/03/2017", "01/04/2017", "event"],
["jane doe", "01/05/2017", "01/06/2017", "event"]]
class ScheduleInfo
attr_reader :name, :date1, :date2, :type
def initialize(*params)
#name, #date1, #date2, #type = params
end
def to_s
format('%s for %s between %s and %s', type, name, date1, date2)
end
end
p info = ScheduleInfo.new('jane', '31/03/2017', '01/04/2017', 'party')
# #<ScheduleInfo:0x00000000d854a0 #name="jane", #date1="31/03/2017", #date2="01/04/2017", #type="party">
puts info.name
# "jane"
schedule_infos = data.map{ |params| ScheduleInfo.new(*params) }
puts schedule_infos
# event for john doe between 01/03/2017 and 01/04/2017
# event for jane doe between 01/05/2017 and 01/06/2017
You can't store the key value pairs in array index. Either you need to just remember that first index of array is gonna have "name" and assign a[0][0] = "foo" or just use array of hashes for the key value functionality you want to have
2.3.0 :006 > a = []
=> []
2.3.0 :007 > hash1 = {name: "hash1name", date: "hash1date", event: "hash1event"}
=> {:name=>"hash1name", :date=>"hash1date", :event=>"hash1event"}
2.3.0 :008 > a << hash1
=> [{:name=>"hash1name", :date=>"hash1date", :event=>"hash1event"}]
2.3.0 :009 > hash2 = {name: "hash2name", date: "hash2date", event: "hash2event"}
=> {:name=>"hash2name", :date=>"hash2date", :event=>"hash2event"}
2.3.0 :010 > a << hash2
=> [{:name=>"hash1name", :date=>"hash1date", :event=>"hash1event"}, {:name=>"hash2name", :date=>"hash2date", :event=>"hash2event"}]
It sounds like you want to call the attribute accessor method that corresponds to each array value. You use send to call methods programmatically. So you need an array of the method names that corresponds to the values you have in your given array. Now, assuming the class with your attributes is called Data.
attrs = [:name, :date1, :date2, :event]
result = a.map do |e|
d = Data.new
e.each.with_index do |v, i|
d.send(attrs[i], v)
end
d
end
The value result is an array of Data objects populated from your given array.
Of course, if you control the definition of your Data object, the best things would be to give it an initialize method that takes an array of values.
Try this:
class Schedule_info
arrt_accessor :name, :date1, :date2, :event
def initialize arr
#name = []
#date1 = []
#date2 = []
#event = []
arr.each |i| do
name << i[0]
date1 << i[1]
date2 << i[2]
event << i[3]
end
end
end