Ruby中是否有nvl()函数,还是我必须自己编写? [英] Is there a nvl() function in Ruby or do I have to write it myself?
问题描述
我想在Ruby中使用等效于Oracle的nvl()
函数.是否有内置函数或我必须自己编写一个函数?
I want to use an equivalent of Oracle's nvl()
function in Ruby. Is there a built in function or do I have to write one myself?
我正在使用它将一些sql重写为ruby:
I am using it to rewrite some sql to ruby:
INSERT INTO my_table (id, val)
VALUES (1, nvl(my_variable,'DEFAULT'));
成为
plsql.my_table.insert {:id => 1, :val => ???my_variable???}
推荐答案
您可以使用有条件的分配
x = find_something() #=>nil
x ||= "default" #=>"default" : value of x will be replaced with "default", but only if x is nil or false
x ||= "other" #=>"default" : value of x is not replaced if it already is other than nil or false
运算符||=
是表达式的简写形式
Operator ||=
is a shorthand form of the expression
x = x || "default"
一些测试
irb(main):001:0> x=nil
=> nil
irb(main):003:0* x||=1
=> 1
irb(main):006:0> x=false
=> false
irb(main):008:0> x||=1
=> 1
irb(main):011:0* x||=2
=> 1
irb(main):012:0> x
=> 1
是的,如果您不希望匹配假,则可以使用Nick Lewis提到的if x.nil?
And yes, If you don't want false to be match, you could use if x.nil?
as Nick Lewis mentioned
irb(main):024:0> x=nil
=> nil
irb(main):026:0* x = 1 if x.nil?
=> 1
修改:
plsql.my_table.insert {:id => 1, :val => ???????}
将是
plsql.my_table.insert {:id => 1, :val => x || 'DEFAULT' }
其中x是在:val中设置的变量名,当x为nil或false时,'DEFAULT'将插入db
where x is the variable name to set in :val, 'DEFAULT' will be insert into db, when x is nil or false
如果您只想将nil设为'DEFAULT',请使用以下方式
If you only want nil to 'DEFAULT', then use following way
{:id => 1, :val => ('DEFAULT' if x.nil?) }
这篇关于Ruby中是否有nvl()函数,还是我必须自己编写?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!