ruby array_Ruby中带有示例的Array.index（）方法

ruby array

Array.index()方法 (Array.index() Method)

In this article, we will study about Array.index() method. You all must be thinking the method must be doing something which is related index of certain element. It is not as simple as it looks. Well, we will figure this out in the rest of our content. We will try to understand it with the help of syntax and demonstrating program codes.

在本文中，我们将研究Array.index()方法 。你们都必须认为方法必须在做某些与某些元素相关的索引的事情。它并不像看起来那么简单。好吧，我们将在其余内容中解决这个问题。我们将尝试借助语法并演示程序代码来理解它。

Method description:

方法说明：

This method is one of the examples of the Public instance method which is specially defined in the Ruby library for Array class. This method is used to find the index of a certain element of the Array instance with the help of the element being passed as the argument. This method works in the way that it returns the index of the first object in Array instance. If you are providing a block instead of an argument then the method will return the index of the first object for which the block returns a Boolean value "True" and returns "nil" if no match is found. This method is one of the examples of non-destructive methods where the changes made by these methods are permanent. There is no destructive version of this method.

此方法是Ruby类库中为Array类专门定义的Public实例方法的示例之一。此方法用于在作为参数传递的元素的帮助下找到Array实例中某个元素的索引。此方法以返回Array实例中第一个对象的索引的方式工作。如果提供的是块而不是参数，则该方法将返回第一个对象的索引，该对象将为其返回布尔值“ True” ，如果找不到匹配项，则返回“ nil” 。此方法是非破坏性方法的示例之一，其中通过这些方法所做的更改是永久性的。此方法没有破坏性版本。

Syntax:

句法：

    array_instance.index()
or
array_instance.index(|item| block)

Argument(s) required:

所需参数：

This method accepts an argument which should be present in the Array instance. This method returns nil if that element is not present in the Array instance.

此方法接受应在Array实例中出现的参数。如果Array实例中不存在该元素，则此方法返回nil。

Example 1:

范例1：

=begin
Ruby program to demonstrate index method
=end	
# array declaration
lang = ["C++","Java","Python","Ruby","Perl"]
puts "Array index implementation."
puts "Enter the element whose index you want to find:"
ele = gets.chomp
if(ind = lang.index(ele))
puts "#{ele} found at index #{ind}"
else
puts "element is not a part of the Array instance"
end

Output

输出量

Array index implementation.
Enter the element whose index you want to find:
Ruby
Ruby found at index 3

Explanation:

说明：

In the above code, you can observe that we are asking the user for the element whose index she wants to find. The user has entered the object "Ruby" which is present in the 3^rd index of the Array instance.

在上面的代码中，您可以观察到我们正在向用户询问要查找其索引的元素。用户已经输入了对象“Ruby”，这是存在于阵列实例的^第三索引。

Example 2:

范例2：

=begin
Ruby program to demonstrate index method
=end	
# array declaration
lang = ["C++","Java","Python","Ruby","Perl"]
puts "Array index implementation."
puts "Enter the element whose index you want to find:"
ele = gets.chomp
if(ind = lang.index{|ind| ind == ele})
puts "#{ele} found at index #{ind}"
else
puts "element is not a part of the Array instance"
end

Output

输出量

Array index implementation.
Enter the element whose index you want to find:
Python
Python found at index 2

Explanation:

说明：

In the above code, you can see that we are passing a block inside the method. The method is returning the index of the first element for which the block stands to be True.

在上面的代码中，您可以看到我们在方法内部传递了一个块。该方法返回该块为True的第一个元素的索引。