Map types

The map counterpart of list_of(T): arbitrary keys, one value type, kept by name – and what a JSON object with arbitrary keys parses into. A failure is reported by key rather than by position.

Usage

map_of(t)

Arguments

t

The value type.

Value

A type.

Details

Reach for list_of(a = T, b = T) instead when the key set is fixed and known up front.

See also

list_of() for an array, or a fixed key set.

Examples

budget <- map_of(int[1][. > 0])
budget(list(cpu = 4, memory = 16))
#> $cpu
#> [1] 4
#> 
#> $memory
#> [1] 16
#> 
try(budget(list(cpu = 4, memory = 0)))
#> Error : 1 validation problem in map_of(int[1][. > 0])
#>   $memory  expected int[1][. > 0], got num[1] 0
try(map_of(int[1])(list(1, 2)))         # unnamed input is list_of(), not this
#> Error : 1 validation problem in map_of(int[1])
#>   <value>  expected map_of(int[1]), got list[2]  -- every key must be named

schema(budget)
#> $type
#> [1] "object"
#> 
#> $additionalProperties
#> $additionalProperties$type
#> [1] "integer"
#> 
#> $additionalProperties$description
#> [1] "satisfies . > 0"
#> 
#> 
from_json(map_of(int[1]), '{"cpu": 4, "memory": 16}')
#> $cpu
#> [1] 4
#> 
#> $memory
#> [1] 16
#>