3.1 KiB
+++ title = "UCG Statements" weight = 4 sort_by = "weight" in_search_index = true +++ Expression Statements
The simplest and least useful is the expression statement. It is any valid expression followed by a semicolon.
1;
4 / 2;
"foo";
"foo" + "bar";
Despite the fact that these are valid the results are thrown away and can essentially be considered a noop.
Named Value Statements
Let statements
There are two statements that can introduce a named value for a given UCG file. Let statements and import statements. Any collisions in binding names inside a file are treated as compile errors. Bindings are immutable and once bound they can't be modified.
let name = "foo";
Import Statement
The import statement imports the contents of another UCG file into the current file
with a name. The imported file's named values are exposed as a tuple in the referencing
file. It starts with the import keyword and is followed by a quoted path to the UCG
file, the keyword as, and a name for the imported values.
import "dbconfigs.ucg" as dbconfigs;
let mysqlconf = dbconfigs.mysql;
Output Statements
Some statements in UCG exist to generate an output. Either a compiled configuration or the results of test assertions.
Assert Statements
The assert statement defines an expression that must evaluate to either true or false.
Assert statements are noops except during a validation compile. They give you a way to
assert certains properties about your data and can be used as a form of unit testing
for your configurations. It starts with the assert keyword followed by a valid block
of UCG statements delimited by | characters. The final statement in the block
must evaluate to a boolean expression.
assert |
host == "www.example.com";
|;
assert |
select qa, 443, {
qa = 80,
prod = 443,
} == 443;
|;
Assert statements are only evaluated when running the ucg test command. That
command evaluates all of the *_test.ucg files. When *_test.ucg files are
run in a test run then ucg will output a log of all the assertions to stdout as
well as a PASS or FAIL for each file. This gives you a simple test harness for
your ucg configs.
Out Statements
The Out statement defines the output for a UCG file. It identifies the output converter type and an expression that will be output. The output converter type is expected to be one of the registered converters unquoted (e.g. json, exec) and the value to convert. The generated artificact will take the same name as the UCG file with the extension replaced by the defined extension for that converter.
For a file named api_config.ucg with the following contents:
let myconf = {
api_url = "https://example.org/api/v1/",
api_token = env.API_TOKEN,
};
out json myconf;
UCG will output the myconf tuple as json to a file called api_config.json
You can get a list of the available converters as well as the extensions
defined for each one by running the ucg converters command.
Next: Converters