Cara Mengatasi Object Variable Or With Block Variable Not Set

Node-red nodes pass the msg object between nodes.

However this object is replaced by the next msg object. So how do you store data between node calls?

Node-Red provides three mechanisms:

• The context object -stores data for a node
• The Flow object – stores data for a flow
• The global object -stores data for the canvas

I will illustrate these methods using a simple flow like the one below.

Post a Question, Get an Answer. Get answers fast from Autodesk support staff and product experts in the forums. Visit Simulation Mechanical forum.

The inject node is used to start the flow , then function node implements the counter and the debug node displays the result.

The idea is to count the number of times the message was injected.

The actual message that gets injected isn’t important.

Note: There is a video to accompany this tutorial as it is easy to demonstrate the interaction between variables using video. You may want to read quickly through the text and then go to the video. Here is the video

Using the Context Object

This is used for storing function variables.

The process for retrieving and storing is to use the get method of the object for retrieving value and the set method to store values.:

A variable stored for function 1 in the context object is not available to function 2 and vice versa.

Initialising the Variable

The standard way is to include this code at the top of the script:

Which means- If count doesn’t exist in the context object then make our local variable count zero; otherwise assign the stored value to our local variable count.

You can use multiple variables e.g.

You can also use an array or an object e.g

In the code above data is an object stored in the context object and local is our local object.

Here is an example script that uses a single variable as a counter in function 1:

Note the above syntax is commonly seen on the Internet but it does cause strange problems due to the way JavaScript identifies True and False.

There instead of

I prefer to use this format:

Here is an example script that uses a object variable as a counter in function 2::

If you look at the code for function 1 and function 2 you will see that they use the same counter variable.

However when you click the inject node for function 1 you see the counter value is 1 and then the inject node for function 2 then counter is also 1.

This shows that the counters are local to each function and not shared between functions.

Note: Currently if you restart the flow the variables are reset but this is likely to change.

Using the Flow Object

You use the flow object in the same way as the context object.

To retrieve values stored in the flow object use:

and to store values use:

This time you should notice that the functions can share variables stored in flow objects. See video

Using the Global Object

You use the flow object in the same way as the context object.

To retrieve values stored in the flow object use:

and to store values use:

This time you should notice that the functions can share variables stored in the global object even across flows.

Video -How to Store Data in Node-Red Variables

Flows Used in the video

Storing and Retrieving Multiple Variables

Activate quickbooks 2019. In node-red version 0.19 it became possible to store and retrieve several variables at once. So instead of using:

If you look at the variables in the store you can see that they are stored as individual variables as shown in the screen shot below. The screen shot also shows how an variable array (data) is stored:

Storing Context Data in The File System

Data stored in the context,flow and glbal variables in known as context data and it is normally stored in memory.

This means that if you restart the flow then the data is lost.

However from version 0.19 it is possible to store the context data in the file system.

In order to do this you will need to modify the settings file and add the following entry:

It doesn’t matter where in the settings file you place it and depending on the version of node-red you started with you may already have an entry that is commented out.

The settings above configure node-red to use the default store in memory and also the filesystem for the filestore.

We therefore have two stores.

When saving data to the context variables or retrieving data from them you will need to specify the store they are in. The default is in memory.

So if you use:

You will retrieve the count variable from memory and to get the count variable from the file store use:

To store data use:

The system stores the variables in a JSON file in a folder called context under the .node-red folder.

Even though you are storing data in the file system it is still possible to loose data as the data is only flushed to the file system every 30 seconds.

You can change this (no real need) and other configuration options see the docs here.

You should also note that you can have two variables with he same name but stored in memory and filesytem as shown in the screen shot below:

Exchange Data Between Nodes Without Wires

With node-red messages are usually passed between nodes using wires.

However it is possible to pass data between nodes with them being wired together using flow and global objects.

Video- Moving Messages between Flows Without Wires

Related tutorials

The java error cannot find symbol occurred when a Compiler does not recognize a class name.

The java error cannot find symbol occurred when a Compiler does not recognize a class name.

The java error cannot find symbol occurred when a Compiler does not recognize a class name. The following are the reason for such an error -

1)When a programmer misspelled the name of the class.

2When a programmer do not Imported the class name.

In this Tutorial we want to describe you a code that help you in understanding java error cannot made symbol. For this we have a class name 'cannot find symbol'. Inside the main method we have initialized a int variable a and b with respective values and store the sum of the value in variable int d.The System.out.println. is used to print the output in variable d in the try block. But in this code the programmer misspelled the variable.,inspite of writing d,the programmer write variable e,The catch block helps you in handling the error occurred in the try block. Therefore the compiler does not recognize a variable e show you an error Java error cannot find symbol.

Here is the video tutorial of 'How to solve cannot find symbol error in Java?':

Cannotfindsymbol.java

import java.lang.*; public class Cannotfindsymbol { public static void main(String[] args) { try{ int a=10; int b=3; int d=a+b; System.out.println(e); } catch(Exception ex){ System.out.println(ex); } } }

Output

/home/girish/NetBeansProjects/errors/src/ Cannotfindsymbol.java:11: cannot find symbol symbol : variable e location: class Cannotfindsymbol System.out.println(e); 1 error0

To remove this error you have to declare the variable e.

Ads

Node-red nodes pass the msg object between nodes.

However this object is replaced by the next msg object. So how do you store data between node calls?

Node-Red provides three mechanisms:

• The context object -stores data for a node
• The Flow object – stores data for a flow
• The global object -stores data for the canvas

I will illustrate these methods using a simple flow like the one below.

Post a Question, Get an Answer. Get answers fast from Autodesk support staff and product experts in the forums. Visit Simulation Mechanical forum.

The inject node is used to start the flow , then function node implements the counter and the debug node displays the result.

The idea is to count the number of times the message was injected.

The actual message that gets injected isn’t important.

Note: There is a video to accompany this tutorial as it is easy to demonstrate the interaction between variables using video. You may want to read quickly through the text and then go to the video. Here is the video

Using the Context Object

This is used for storing function variables.

The process for retrieving and storing is to use the get method of the object for retrieving value and the set method to store values.:

A variable stored for function 1 in the context object is not available to function 2 and vice versa.

Initialising the Variable

The standard way is to include this code at the top of the script:

Which means- If count doesn’t exist in the context object then make our local variable count zero; otherwise assign the stored value to our local variable count.

You can use multiple variables e.g.

You can also use an array or an object e.g

In the code above data is an object stored in the context object and local is our local object.

Here is an example script that uses a single variable as a counter in function 1:

Note the above syntax is commonly seen on the Internet but it does cause strange problems due to the way JavaScript identifies True and False.

There instead of

I prefer to use this format:

Here is an example script that uses a object variable as a counter in function 2::

If you look at the code for function 1 and function 2 you will see that they use the same counter variable.

However when you click the inject node for function 1 you see the counter value is 1 and then the inject node for function 2 then counter is also 1.

This shows that the counters are local to each function and not shared between functions.

Note: Currently if you restart the flow the variables are reset but this is likely to change.

Using the Flow Object

You use the flow object in the same way as the context object.

To retrieve values stored in the flow object use:

and to store values use:

This time you should notice that the functions can share variables stored in flow objects. See video

Using the Global Object

You use the flow object in the same way as the context object.

To retrieve values stored in the flow object use:

and to store values use:

This time you should notice that the functions can share variables stored in the global object even across flows.

Video -How to Store Data in Node-Red Variables

Flows Used in the video

Storing and Retrieving Multiple Variables

Activate quickbooks 2019. In node-red version 0.19 it became possible to store and retrieve several variables at once. So instead of using:

If you look at the variables in the store you can see that they are stored as individual variables as shown in the screen shot below. The screen shot also shows how an variable array (data) is stored:

Storing Context Data in The File System

Data stored in the context,flow and glbal variables in known as context data and it is normally stored in memory.

This means that if you restart the flow then the data is lost.

However from version 0.19 it is possible to store the context data in the file system.

In order to do this you will need to modify the settings file and add the following entry:

It doesn’t matter where in the settings file you place it and depending on the version of node-red you started with you may already have an entry that is commented out.

The settings above configure node-red to use the default store in memory and also the filesystem for the filestore.

We therefore have two stores.

When saving data to the context variables or retrieving data from them you will need to specify the store they are in. The default is in memory.

So if you use:

You will retrieve the count variable from memory and to get the count variable from the file store use:

To store data use:

The system stores the variables in a JSON file in a folder called context under the .node-red folder.

Even though you are storing data in the file system it is still possible to loose data as the data is only flushed to the file system every 30 seconds.

You can change this (no real need) and other configuration options see the docs here.

You should also note that you can have two variables with he same name but stored in memory and filesytem as shown in the screen shot below:

Exchange Data Between Nodes Without Wires

With node-red messages are usually passed between nodes using wires.

However it is possible to pass data between nodes with them being wired together using flow and global objects.

Video- Moving Messages between Flows Without Wires

Related tutorials

The java error cannot find symbol occurred when a Compiler does not recognize a class name.

The java error cannot find symbol occurred when a Compiler does not recognize a class name.

The java error cannot find symbol occurred when a Compiler does not recognize a class name. The following are the reason for such an error -

1)When a programmer misspelled the name of the class.

2When a programmer do not Imported the class name.

In this Tutorial we want to describe you a code that help you in understanding java error cannot made symbol. For this we have a class name 'cannot find symbol'. Inside the main method we have initialized a int variable a and b with respective values and store the sum of the value in variable int d.The System.out.println. is used to print the output in variable d in the try block. But in this code the programmer misspelled the variable.,inspite of writing d,the programmer write variable e,The catch block helps you in handling the error occurred in the try block. Therefore the compiler does not recognize a variable e show you an error Java error cannot find symbol.

Here is the video tutorial of 'How to solve cannot find symbol error in Java?':

Cannotfindsymbol.java

import java.lang.*; public class Cannotfindsymbol { public static void main(String[] args) { try{ int a=10; int b=3; int d=a+b; System.out.println(e); } catch(Exception ex){ System.out.println(ex); } } }

Output

/home/girish/NetBeansProjects/errors/src/ Cannotfindsymbol.java:11: cannot find symbol symbol : variable e location: class Cannotfindsymbol System.out.println(e); 1 error0

To remove this error you have to declare the variable e.

Ads