Ruby/Statement/If
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Версия от 18:00, 13 сентября 2010; ViGOur (Обсуждение | вклад)
An if statement with an else clause looks like in general (the else clause is optional)
if Boolean [then | :] code [else code ] end
Conditional Statements
value = 0 if value.zero? then puts "value is zero. Did you guess that one?" end
if and unless also supply the else condition
# used to delimit lines of code that you want to be executed if the main expression is false: age = 10 if age < 18 puts "You"re too young to use this system" else puts "You can use this system" end
if statement contains several elsif statements
lang = :es if lang == :en print "dog" elsif lang == :es print "perro" elsif lang == :fr print "chien" elsif lang == :de print "Hund" else puts "No language set; default = "dog"." end # "perro" is assigned to dog
lay out an if statement is by replacing the then with a colon (:)
x = 256 if x == 256: puts "x equals 256" end
nest if logic
age = 19 if age < 21 puts "You can"t drink in most of the United States" if age >= 18 puts "But you can in the United Kingdom!" end end
put any number of lines of code in between the if statement and the end line:
age = 10 if age < 18 puts "You"re too young to use this system" puts "So we"re going to exit your program now" exit end
Syntax of using elsif Clauses in if Statements
if (condition1) code to be executed if condition1 is true elsif (condition2) code to be executed if condition2 is true else code to be executed if condition1 and condition2 are not true
The if Statement with constant
if 1 == 1 then print "True!" end
The simple form of an if statement looks like this
if Boolean [then | :] code end
Use an elsif Clause
temperature = 76 if temperature > 85 puts "Too hot!" elsif temperature < 65 puts "Too cold!" else puts "Picnic time!" end
Use if statement to check the user input
print "(t)imes or (p)lus: " times = gets print "number: " number = Integer(gets) if times =~ /^t/ puts((1..10).collect {|n| n*number }.join(", ")) else puts((1..10).collect {|n| n+number }.join(", ")) end
Use the if Statement
temperature = 76 if temperature > 65 && temperature < 85 puts "Picnic time!" end
use the ! logical negation operator
temperature = 76 if !(temperature < 65 || temperature > 85) puts "Picnic time!" else puts "Sorry, no picnic today." end
use the multiline if/else option
age = 10 if age < 18 type = "child" else type = "adult" end puts "You are a " + type
Using else Clauses in if Statements
temperature = 43 if temperature > 65 && temperature < 85 puts "Picnic time!" else puts "Sorry, no picnic today." end
we dropped then from the if statement.
# In addition, you don"t have to use end if you write this code all on one line, like so: x = 256 if x == 256 then puts "x equals 256" end
write elsif statement a little tighter by using colons after the symbols:
if lang == :en: print "dog" elsif lang == :es: print "perro" elsif lang == :fr: print "chien" elsif lang == :de: print "Hund" else puts "No language set; default = "dog"." end
