ReQL command: branch

Command syntax

r.branch(test, true_action[, test2, test2_action, ...], false_action) → any
test.branch(true_action[, test2, test2_action, ...], false_action) → any

Description

Perform a branching conditional equivalent to if-then-else.

The branch command takes 2n+1 arguments: pairs of conditional expressions and commands to be executed if the conditionals return any value but False or None (i.e., “truthy” values), with a final “else” command to be evaluated if all of the conditionals are False or None.

You may call branch infix style on the first test. (See the second example for an illustration.)

r.branch(test1, val1, test2, val2, elseval)

is the equivalent of the Python statement

if test1:
    return val1
elif test2:
    return val2
else:
    return elseval

Example: Test the value of x.

x = 10
r.branch((x > 5), 'big', 'small').run(conn)

> "big"

Example: As above, infix-style.

x = 10
r.expr(x > 5).branch('big', 'small').run(conn)

> "big"

Example: Categorize heroes by victory counts.

r.table('marvel').map(
    r.branch(
        r.row['victories'] > 100,
        r.row['name'] + ' is a superhero',
        r.row['victories'] > 10,
        r.row['name'] + ' is a hero',
        r.row['name'] + ' is very nice'
    )
).run(conn)

If the documents in the table marvel are:

[
    { "name": "Iron Man", "victories": 214 },
    { "name": "Jubilee", "victories": 49 },
    { "name": "Slava", "victories": 5 }
]

The results will be:

[
    "Iron Man is a superhero",
    "Jubilee is a hero",
    "Slava is very nice"
]

Related commands

• do

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