$ lein run -m systems.simple-system1/mainLiking cljdoc? Tell your friends :D
Very Simple System
First of all let’s create a very simple component with just one dependency to have a minimum working environment.
In order to execute the following example from the hellhound_examples repository. Just issue the following command in the repository root directory.
Ok let’s jump into the code.
link:simple_system1.clj[role=include]| 1 | The start function of the component 1 which will assign to the component later in the component map. The first argument is the componet map itself and the argument is the context map which contains extra info about the context which this component is running on. As you already know start function of a component should return a component map. |
| 2 | Assinged a simple value to a key in component map. So the running component would have this value attached to it and other components can use the value by getting it from the component map. |
| 3 | Stop function of the component1. It should returns a component map. |
| 4 | Start function of component-2. |
| 5 | Gets the first dependency component. In the order which defined in the
component map :depends-on |
| 6 | Gets the same component by it’s name instead. |
| 7 | Gets a value from another component. |
| 8 | A component map which defines the :simple-system/component-1 component
Intentionally we defined this component by defining a map directly.
But you can use defcomponent function as a shortcut. |
| 9 | We used defcomponent to define a component called :simple-system/component-2.
It basically returns a map like we had in component-1 with the given details. |
| 10 | A very simple system defination which does not have any workflow.
Please not that the order of components in :components vector is
NOT important at all. |
| 11 | Setting the simple-system as the default system of the application. |
| 12 | Start the default system. |
The last argument is the dependency vector of the component that exactly is
going to be the :depends-on key in the component map.
|
When we execute the above code the output would be something like:
The output of the above namespace
[17-10-29 12:27:37] [DEBUG] <hellhound.component:115> - Starting component ':simple-system/component-1'... (1)
Starting Component 1... (2)
[17-10-29 12:27:37] [DEBUG] <hellhound.component:115> - Starting component ':simple-system/component-2'...
Starting Component 2... (3)
Hello World (4)
Hello World (5)
[17-10-29 12:27:37] [DEBUG] <hellhound.component:120> - Component ':simple-system/component-1' already started. Skipping... (6)
[17-10-29 12:27:37] [INFO] <hellhound.system.core:142> - System started successfully. (7)
[17-10-29 12:27:37] [DEBUG] <hellhound.system.workflow:104> - Setting up workflow...
[17-10-29 12:27:37] [INFO] <hellhound.system.workflow:107> - Workflow setup done.| 1 | A log entry with DEBUG level states that HellHound is going to start :simple-system/component-1 |
| 2 | The output of the println in line of [6] of the above code. |
| 3 | The output of the println in line of [18] of the above code. |
| 4 | The output of the println function in the start function of th :simple-system/component-2 |
| 5 | Same as number 4. |
| 6 | A log entry which states that :simple-system/component-1 is already running and HellHound is going to skipp it. |
| 7 | System started at this point completely. |
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