Instantiate Schema class

Factory method to instantiate Schema class. This method is async and it should be used with value keyword from future package.

Schema.load(descriptor, strict=FALSE, caseInsensitiveHeaders = FALSE)

Arguments

descriptor	schema descriptor, a JSON string, URL or file
strict	flag to alter validation behaviour: if FALSE error will not be raised and all error will be collected in schema$errors if TRUE any validation error will be raised immediately
caseInsensitiveHeaders	default is set to FALSE

Value

Schema class object

See also

Schema, Table Schema Specifications

Examples

SCHEMA <- '{"fields": [
  {"name": "id", "type": "string", "constraints": {"required": true}},
  {"name": "height", "type": "number"},
  {"name": "age", "type": "integer"},
  {"name": "name", "type": "string", "constraints": {"required": true}},
  {"name": "occupation", "type": "string"}
  ]}'

# instantiate Schema class
def  = Schema.load(descriptor = SCHEMA)
schema = future::value(def)

# correct number of fields
length(schema$fields)
#> [1] 5

# correct field names
schema$fieldNames
#> [[1]]
#> [1] "id"
#> 
#> [[2]]
#> [1] "height"
#> 
#> [[3]]
#> [1] "age"
#> 
#> [[4]]
#> [1] "name"
#> 
#> [[5]]
#> [1] "occupation"
#> 

# convert row
row = list('string', '10.0', '1', 'string', 'string')
castRow = schema$castRow(row)
castRow
#> [[1]]
#> [1] "string"
#> 
#> [[2]]
#> [1] 10
#> 
#> [[3]]
#> [1] 1
#> 
#> [[4]]
#> [1] "string"
#> 
#> [[5]]
#> [1] "string"
#> 

SCHEMA_MIN <- '{
"fields": [
  {"name": "id"},
  {"name": "height"}
  ]}'

# load schema
def2  = Schema.load(descriptor = SCHEMA_MIN)
schema2 = future::value(def2)

# set default types if not provided
schema2$fields[[1]]$type
#> [1] "string"
schema2$fields[[2]]$type
#> [1] "string"

# fields are not required by default
schema2$fields[[1]]$required
#> [1] FALSE
schema2$fields[[2]]$required
#> [1] FALSE


#work in strict mode
descriptor = '{"fields": [{"name": "name", "type": "string"}]}'
def3  = Schema.load(descriptor = descriptor, strict = TRUE)
schema3 = future::value(def3)
schema3$valid
#> [1] TRUE

# work in non-strict mode
descriptor = '{"fields": [{"name": "name", "type": "string"}]}'
def4 = Schema.load(descriptor = descriptor, strict = FALSE)
schema4 = future::value(def4)
schema4$valid
#> [1] TRUE

# work with primary/foreign keys as arrays
descriptor2 = '{
"fields": [{"name": "name"}],
"primaryKey": ["name"],
"foreignKeys": [{
  "fields": ["parent_id"],
  "reference": {"resource": "resource", "fields": ["id"]}
}]}'

def5 = Schema.load(descriptor2)
schema5 = future::value(def5)

schema5$primaryKey
#> [[1]]
#> [1] "name"
#> 
schema5$foreignKeys
#> [[1]]
#> [[1]]$fields
#> [[1]]$fields[[1]]
#> [1] "parent_id"
#> 
#> 
#> [[1]]$reference
#> [[1]]$reference$resource
#> [1] "resource"
#> 
#> [[1]]$reference$fields
#> [[1]]$reference$fields[[1]]
#> [1] "id"
#> 
#> 
#> 
#> 


# work with primary/foreign keys as string
descriptor3 = '{
"fields": [{"name": "name"}],
"primaryKey": "name",
"foreignKeys": [{
  "fields": "parent_id",
  "reference": {"resource": "resource", "fields": "id"}
}]}'

def6 = Schema.load(descriptor3)
schema6 = future::value(def6)
schema6$primaryKey
#> [[1]]
#> [1] "name"
#> 
schema6$foreignKeys
#> [[1]]
#> [[1]]$fields
#> [[1]]$fields[[1]]
#> [1] "parent_id"
#> 
#> 
#> [[1]]$reference
#> [[1]]$reference$resource
#> [1] "resource"
#> 
#> [[1]]$reference$fields
#> [[1]]$reference$fields[[1]]
#> [1] "id"
#> 
#> 
#> 
#>