value assignment in groovy

Monday, February 12, 2018

Groovy: basic concepts: variables, storage and commands, simple variables, composite variables, copy and reference, assignments, sequential commands, conditional commands, switch-case, iterative commands, each and eachwithindex, expressions with side effects, no comments:.

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Groovy Variable Scope

Last updated: February 13, 2024

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1. Introduction

In this tutorial, we’ll talk about how to work with the different Groovy scopes and see how we can take advantage of its variable scope

2. Dependencies

Throughout, we’ll use the  groovy-all and spock-core  dependencies

3. All Scopes

Scopes in Groovy follow, above all, the rule that all variables are created public by default . This means that, unless specified, we’ll be able to access any variable we created from any other scope in the code.

We will see what these scopes mean and to tests this we will run Groovy scripts . To run a script we only need to run:

3.1. Global Variables

The easiest way to create a global variable in a Groovy script is to assign it anywhere in the script without any special keywords. We don’t even need to define the type:

Then, if we run the following groovy script:

we’ll see that we can reach our variable from the global scope.

3.2. Accessing Global Variables from Function Scope

Another way of accessing a global variable is by using the function scope:

This function is defined within the scope script. We add 1 to our global x variable.

If we run the following script:

We will get 201 as a result. This proves that we can access our global variable from the local scope of a function.

3.3. Creating Global Variables from a Function Scope

We can also create global variables from inside a function scope. In this local scope, if we don’t use any keyword in creating the variable, we’ll create it in the global scope. Let’s, then, create a global variable  z in a new function:

and try and access it by running the following script:

We will see that we can access z from the global scope. So this finally proves that our variable has been created in the global scope.

3.4. Non-Global Variables

In the case of non-global variables, we’ll have a quick look at variables created for the local scope only.

Specifically, we’ll be looking at keyword def . This way, we define this variable to be part of the scope where the thread is running.

So, let’s try and define a global variable y and a function-local variable:

If we run this script, it will fail. The reason why it’s failing is that q is a local variable, which belongs to the scope of function  fLocal . Since we create  q with the def keyword, we won’t be able to access it via the global scope.

Evidently, we can access q using the fLocal  function:

So now we can see that even though we have created one  q  variable, that variable isn’t available anymore in other scopes. If we call  fLocal again, we’ll just create a new variable.

4. Conclusion

In this article, we have seen how Groovy scopes are created and how they can be accessed from different areas in the code.

As always, the full source code for the examples is available  over on GitHub .

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Variables are like containers which holds the data values. A variable specifies the name of the memory location.

How to declare variables

There are three ways to declare variables in Groovy.

• Native syntax similar to Java
• Using def keyword
• Variables in groovy do not require a type definition.

In the above syntax, assigning value is optional as you can just declare the variable and then assign value at later point in the program. Also, the value of a variable can be changed at any time.

Naming convention of variables

• Variable's name should consists of only letters (both uppercase and lowercase letters), digits and underscore( _ ).
• Variable's name cannot contain white spaces like first name which is a invalid variable name.
• First letter of a variable should be either a letter or an underscore( _ ).
• Variable names are case sensitive and hence Name and name both are different.
• It is always advisable to give some meaningful names to variables.

The above can also be written like below

Sample program:

Check result here.

September 1, 2009

Groovy goodness: multiple assignments.

Since Groovy 1.6 we can define and assign values to several variables at once. This is especially useful when a method returns multiple values and we want to assign them to separate variables.

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Field Value Assignment Methods

Values from fields are pulled into variables or even other fields by 2 possible methods:

1) Direct Assignment

The simplest and most direct way of getting the value of a field is by using the assignment operator to put the value from the field into a variable by utilizing the field API name.

On opportunities, the name of the opportunity has its API name as Name. We just do:

If we have a custom field, the API name of a custom field is FieldName_c (custom fields always have a _c )

The variable will take the data type of the field we assign to it. So if the field is a numeric field, the variable will also be a numeric variable.

2) Using a Get Method

Groovy in Sales Cloud provides several get methods to pull values from fields:

• getAttribute()
• getSelectedListDisplayValue()
• getSelectedListDisplayValues()
• getOriginalAttributeValue()

These methods belong to the Row class, which is part of the ADF framework on which Fusion is built.

Note: These get methods always return a String. This is important because, as we will learn in later tutorials, when assigning values to fields or variables, we must respect their data types.

From all the methods listed above, the most used are getAttribute() and getSelectedListDisplayValue() .

We use getAttribute() to pull values from all fields. For example, if we have a text field like the Name field of opportunities and we want to get its value, we would do:

If we want to assign this value to a variable, we would first define a variable and then use the assignment operator to put the value of the Name field into it:

Let's see another example:

If we are in, let's say, a trigger on the opportunity object and we want to get the value of a field called Comments, we type the following code:

When we want to save our work, we get this warning: Some fields whose value may be null are not protected by the nvl() function: Comments.

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Groovy value types

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Declare variables with def

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Published on 2018-05-27

Author: Gabor Szabo

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Variable Assignment and Groovy : Or how i learned to hate code and start drinking.

First and foremost i want to list that i am not a developer.

I am an automation engineer and i spend 99% of my day writing code in PowerShell and Python.

I would consider myself an expert in PowerShell and competent in Python. I have had to start learning Groovy to put together some pipelines in Jenkins and i am running into some issues where variables are scoped in ways i don't seem to understand.

Below are some examples :

The output is :

When i extend this code two a second stage weird things start happening.

I get the following output :

Now, i am aware this might not be Groovy related and it may have something to with how jenkins implements Pipelines but why on earth does a variable i declare like value2 work in the next stage and the value i declare with 'def' not work in the next stage?

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1.1. Normal arithmetic operators

1.2. unary operators, 1.3. assignment arithmetic operators, 2. relational operators, 3.1. precedence, 3.2. short-circuiting, 4. bitwise operators, 5.1. not operator, 5.2. ternary operator, 5.3. elvis operator, 6.1. safe navigation operator, 6.2. direct field access operator, 6.3. method pointer operator, 7.1. pattern operator, 7.2. find operator, 7.3. match operator, 8.1.1. spreading method arguments, 8.1.2. spread list elements, 8.1.3. spread map elements, 8.2. range operator, 8.3. spaceship operator, 8.4. subscript operator, 8.5. membership operator, 8.6. identity operator, 8.7. coercion operator, 8.8. diamond operator, 8.9. call operator, 9. operator precedence, 10. operator overloading.

This chapter covers the operators of the Groovy programming language.

1. Arithmetic operators

Groovy supports the usual familiar arithmetic operators you find in mathematics and in other programming languages like Java. All the Java arithmetic operators are supported. Let’s go through them in the following examples.

The following binary arithmetic operators are available in Groovy:

Here are a few examples of usage of those operators:

The + and - operators are also available as unary operators:

In terms of unary arithmetics operators, the ++ (increment) and -- (decrement) operators are available, both in prefix and postfix notation:

From the binary arithmetic operators we have seen above, certain of them are also available in an assignment form:

Let’s see them in action:

Relational operators allow comparisons between objects, to know if two objects are the same or different, or if one is greater than, less than, or equal to the other.

The following operators are available:

Here are some examples of simple number comparisons using these operators:

3. Logical operators

Groovy offers three logical operators for boolean expressions:

&& : logical "and"

|| : logical "or"

! : logical "not"

Let’s illustrate them with the following examples:

The logical "not" has a higher priority than the logical "and".

The logical "and" has a higher priority than the logical "or".

The logical || operator supports short-circuiting: if the left operand is true, it knows that the result will be true in any case, so it won’t evaluate the right operand. The right operand will be evaluated only if the left operand is false.

Likewise for the logical && operator: if the left operand is false, it knows that the result will be false in any case, so it won’t evaluate the right operand. The right operand will be evaluated only if the left operand is true.

Groovy offers 4 bitwise operators:

& : bitwise "and"

| : bitwise "or"

^ : bitwise "xor" (exclusive "or")

~ : bitwise negation

Bitwise operators can be applied on a byte or an int and return an int :

It’s worth noting that the internal representation of primitive types follow the Java Language Specification . In particular, primitive types are signed, meaning that for a bitwise negation, it is always good to use a mask to retrieve only the necessary bits.

In Groovy, bitwise operators have the particularity of being overloadable , meaning that you can define the behavior of those operators for any kind of object.

5. Conditional operators

The "not" operator is represented with an exclamation mark ( ! ) and inverts the result of the underlying boolean expression. In particular, it is possible to combine the not operator with the Groovy truth :

The ternary operator is a shortcut expression that is equivalent to an if/else branch assigning some value to a variable.

Instead of:

You can write:

The ternary operator is also compatible with the Groovy truth , so you can make it even simpler:

The "Elvis operator" is a shortening of the ternary operator. One instance of where this is handy is for returning a 'sensible default' value if an expression resolves to false or null . A simple example might look like this:

Usage of the Elvis operator reduces the verbosity of your code and reduces the risks of errors in case of refactorings, by removing the need to duplicate the expression which is tested in both the condition and the positive return value.

6. Object operators

The Safe Navigation operator is used to avoid a NullPointerException . Typically when you have a reference to an object you might need to verify that it is not null before accessing methods or properties of the object. To avoid this, the safe navigation operator will simply return null instead of throwing an exception, like so:

Normally in Groovy, when you write code like this:

The user.name call triggers a call to the property of the same name, that is to say, here, to the getter for name . If you want to retrieve the field instead of calling the getter, you can use the direct field access operator:

The method pointer operator ( .& ) call be used to store a reference to a method in a variable, in order to call it later:

There are multiple advantages in using method pointers. First of all, the type of such a method pointer is a groovy.lang.Closure , so it can be used in any place a closure would be used. In particular, it is suitable to convert an existing method for the needs of the strategy pattern:

Method pointers are bound by the receiver and a method name. Arguments are resolved at runtime, meaning that if you have multiple methods with the same name, the syntax is not different, only resolution of the appropriate method to be called will be done at runtime:

7. Regular expression operators

The pattern operator ( ~ ) provides a simple way to create a java.util.regex.Pattern instance:

while in general, you find the pattern operator with an expression in a slashy-string, it can be used with any kind of String in Groovy:

Alternatively to building a pattern, you can directly use the find operator =~ to build a java.util.regex.Matcher instance:

Since a Matcher coerces to a boolean by calling its find method, the =~ operator is consistent with the simple use of Perl’s =~ operator, when it appears as a predicate (in if , while , etc.).

The match operator ( ==~ ) is a slight variation of the find operator, that does not return a Matcher but a boolean and requires a strict match of the input string:

8. Other operators

8.1. spread operator.

The Spread Operator ( *. ) is used to invoke an action on all items of an aggregate object. It is equivalent to calling the action on each item and collecting the result into a list:

The spread operator is null-safe, meaning that if an element of the collection is null, it will return null instead of throwing a NullPointerException :

The spread operator can be used on any class which implements the Iterable interface:

There may be situations when the arguments of a method call can be found in a list that you need to adapt to the method arguments. In such situations, you can use the spread operator to call the method. For example, imagine you have the following method signature:

then if you have the following list:

you can call the method without having to define intermediate variables:

It is even possible to mix normal arguments with spread ones:

When used inside a list literal, the spread operator acts as if the spread element contents were inlined into the list:

The spread map operator works in a similar manner as the spread list operator, but for maps. It allows you to inline the contents of a map into another map literal, like in the following example:

The position of the spread map operator is relevant, like illustrated in the following example:

Groovy supports the concept of ranges and provides a notation ( .. ) to create ranges of objects:

Ranges implementation is lightweight, meaning that only the lower and upper bounds are stored. You can create a range from any Comparable object. For example, you can create a range of characters this way:

The spaceship operator ( ) delegates to the compareTo method:

The subscript operator is a short hand notation for getAt or putAt , depending on whether you find it on the left hand side or the right hand side of an assignment:

The subscript operator, in combination with a custom implementation of getAt / putAt is a convenient way for destructuring objects:

The membership operator ( in ) is equivalent to calling the isCase method. In the context of a List , it is equivalent to calling contains , like in the following example:

In Groovy, using == to test equality is different from using the same operator in Java. In Groovy, it is calling equals . If you want to compare reference equality, you should use is like in the following example:

The coercion operator ( as ) is a variant of casting. Coercion converts object from one type to another without them being compatible for assignment. Let’s take an example:

This can be fixed by using coercion instead:

When an object is coerced into another, unless the target type is the same as the source type, coercion will return a new object. The rules of coercion differ depending on the source and target types, and coercion may fail if no conversion rules are found. Custom conversion rules may be implemented thanks to the asType method:

The diamond operator ( <> ) is a syntactic sugar only operator added to support compatibility with the operator of the same name in Java 7. It is used to indicate that generic types should be inferred from the declaration:

In dynamic Groovy, this is totally unused. In statically type checked Groovy, it is also optional since the Groovy type checker performs type inference whether this operator is present or not.

The call operator () is used to call a method named call implicitly. For any object which defines a call method, you can omit the .call part and use the call operator instead:

The table below lists all groovy operators in order of precedence.

Groovy allows you to overload the various operators so that they can be used with your own classes. Consider this simple class:

Just by implementing the plus() method, the Bucket class can now be used with the + operator like so:

All (non-comparator) Groovy operators have a corresponding method that you can implement in your own classes. The only requirements are that your method is public, has the correct name, and has the correct number of arguments. The argument types depend on what types you want to support on the right hand side of the operator. For example, you could support the statement

by implementing the plus() method with this signature:

Here is a complete list of the operators and their corresponding methods:

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How to assign values to array using groovy?

I want to extract the all name from response and assign it to array/list?

It is retrieving the first row, name (i.e) vicky only.. i wanted to extract name of all rows and assign it to list.. How to do this?

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