Merge pull request #21 from frictionlessdata/Go11PlusReadColumn

Add support to go 1.11 and go modules.

Author: danielfireman

.travis.yml

@@ -4,14 +4,19 @@ go:
  - 1.8.x
  - 1.9.x
  - 1.10.x
-
+ - 1.11.x
 notificaitons:
   email:
     recipients: [email protected]
     on_success: change
     on_failure: always
 
+env:
+  - GO111MODULE=on
+
 before_install:
+  - curl https://raw.githubusercontent.com/golang/dep/master/install.sh | sh  
+  - dep ensure
   - go get github.com/mattn/goveralls
 
 script:

Gopkg.lock

@@ -3,21 +3,17 @@
 # datapackage-go
 A Go library for working with [Data Packages](http://specs.frictionlessdata.io/data-package/).
 
-<!-- TOC -->
-
 - [datapackage-go](#datapackage-go)
-    - [Install](#install)
-    - [Main Features](#main-features)
-        - [Loading and validating tabular data package descriptors](#loading-and-validating-tabular-data-package-descriptors)
-        - [Accessing data package resources](#accessing-data-package-resources)
-        - [Loading zip bundles](#loading-zip-bundles)
-        - [Creating a zip bundle with the data package.](#creating-a-zip-bundle-with-the-data-package)
-        - [CSV dialect support](#csv-dialect-support)
-        - [Loading multipart resources](#loading-multipart-resources)
-        - [Loading non-tabular resources](#loading-non-tabular-resources)
-        - [Manipulating data packages programatically](#manipulating-data-packages-programatically)
-
-<!-- /TOC -->
+     - [Install](#install)
+     - [Main Features](#main-features)
+         - [Loading and validating tabular data package descriptors](#loading-and-validating-tabular-data-package-descriptors)
+         - [Accessing data package resources](#accessing-data-package-resources)
+         - [Loading zip bundles](#loading-zip-bundles)
+         - [Creating a zip bundle with the data package.](#creating-a-zip-bundle-with-the-data-package)
+         - [CSV dialect support](#csv-dialect-support)
+         - [Loading multipart resources](#loading-multipart-resources)
+         - [Loading non-tabular resources](#loading-non-tabular-resources)
+         - [Manipulating data packages programatically](#manipulating-data-packages-programatically)
 
 ## Install
 
@@ -95,7 +91,7 @@ fmt.Printf("+v", cities)
 // [{City:london Year:2017 Population:8780000} {City:paris Year:2017 Population:2240000} {City:rome Year:2017 Population:2860000}]
 ```
 
-Finally, if the data is to big to be loaded at once or if you would like to perform line-by-line processing, you could iterate through the resource contents:
+If the data is to big to be loaded at once or if you would like to perform line-by-line processing, you could iterate through the resource contents:
 
 ```go
 iter, _ := resource.Iter(csv.LoadHeaders())
@@ -109,6 +105,16 @@ for iter.Next() {
 // {City:paris Year:2017 Population:2240000}
 // {City:rome Year:2017 Population:2860000}]
 ```
+
+Or you might want to process specific columns, for instance to perform an statical analysis:
+
+```go
+var population []float64
+resource.CastColumn("population", &population, csv.LoadHeaders())
+fmt.Println(ages)
+// Output: [8780000 2240000 2860000]
+```
+
 ### Loading zip bundles
 
 It is very common to store the data in zip bundles containing the descriptor and data files. Those are natively supported by our the [datapackage.Load](https://godoc.org/github.com/frictionlessdata/datapackage-go/datapackage#Load) method. For example, lets say we have the following `package.zip` bundle:

README.md

@@ -343,6 +343,25 @@ func (r *Resource) Cast(out interface{}, opts ...csv.CreationOpts) error {
 	return sch.CastTable(tbl, out)
 }
 
+// CastColumn casts a column from tabular resource contents.
+// The out argument must necessarily be the address for a slice. The slice
+// may be nil or previously allocated.
+func (r *Resource) CastColumn(name string, out interface{}, opts ...csv.CreationOpts) error {
+	sch, err := r.GetSchema()
+	if err != nil {
+		return err
+	}
+	tab, err := r.GetTable(opts...)
+	if err != nil {
+		return err
+	}
+	col, err := tab.ReadColumn(name)
+	if err != nil {
+		return err
+	}
+	return sch.CastColumn(col, name, out)
+}
+
 // NewResourceWithDefaultRegistry creates a new Resource from the passed-in descriptor.
 // It uses the default registry to validate the resource descriptor.
 func NewResourceWithDefaultRegistry(d map[string]interface{}) (*Resource, error) {

datapackage/resource.go

@@ -10,9 +10,27 @@ import (
 	"testing"
 
 	"github.com/frictionlessdata/datapackage-go/validator"
+	"github.com/frictionlessdata/tableschema-go/csv"
+	"github.com/frictionlessdata/tableschema-go/schema"
 	"github.com/matryer/is"
 )
 
+func ExampleResource_CastColumn() {
+	resStr := `
+	{
+		"name":    "col",
+		"data":    "name,age\nfoo,42\nbar,84",
+		"format":  "csv",
+		"profile": "tabular-data-resource",
+		"schema": {"fields": [{"name": "name", "type": "string"},{"name": "age", "type": "integer"}]}
+	}`
+	res, _ := NewResourceFromString(resStr, validator.MustInMemoryRegistry())
+	var ages []float64
+	res.CastColumn("age", &ages, csv.LoadHeaders())
+	fmt.Println(ages)
+	// Output: [42 84]
+}
+
 func TestNewResourceWithDefaultRegistry(t *testing.T) {
 	res, _ := NewResourceWithDefaultRegistry(r1)
 	fmt.Println(res.Name())
@@ -152,9 +170,9 @@ func TestNew(t *testing.T) {
 				map[string]interface{}{"name": "foo", "path": "foo.csv", "schema": ts.URL},
 				validator.MustInMemoryRegistry(),
 			)
-			is.NoErr(err)
+			is.NoErr(err) // Resource should be created successfully.
 			sch, err := r.GetSchema()
-			is.Equal(sch.Fields[0].Type, "string")
+			is.Equal(sch.Fields[0].Type, schema.StringType)
 		})
 		t.Run("InvalidRemote", func(t *testing.T) {
 			_, err := NewResource(
@@ -177,7 +195,7 @@ func TestNew(t *testing.T) {
 			)
 			is.NoErr(err)
 			sch, err := r.GetSchema()
-			is.Equal(sch.Fields[0].Type, "string")
+			is.Equal(sch.Fields[0].Type, schema.StringType)
 		})
 		t.Run("InvalidLocal", func(t *testing.T) {
 			_, err := NewResource(
@@ -457,3 +475,65 @@ func TestResource_RawRead(t *testing.T) {
 		is.Equal(string(contents), "{\"foo\":\"1234\"}")
 	})
 }
+
+func TestResource_ReadColumn(t *testing.T) {
+	resStr := `
+			{
+				"name":    "col",
+				"data":    "name,age\nfoo,42\nbar,84",
+				"format":  "csv",
+				"profile": "tabular-data-resource",
+				"schema": {"fields": [{"name": "name", "type": "string"},{"name": "age", "type": "integer"}]}
+			}`
+	t.Run("Valid", func(t *testing.T) {
+		is := is.New(t)
+		res, err := NewResourceFromString(resStr, validator.MustInMemoryRegistry())
+		is.NoErr(err)
+		var ages []float64
+		is.NoErr(res.CastColumn("age", &ages, csv.LoadHeaders()))
+		is.Equal(float64(42), ages[0])
+		is.Equal(float64(84), ages[1])
+	})
+	t.Run("NoSchema", func(t *testing.T) {
+		res := NewUncheckedResource(map[string]interface{}{})
+		var ages []float64
+		if res.CastColumn("age", &ages) == nil {
+			t.Fatal("want:err got:nil")
+		}
+	})
+	t.Run("NoData", func(t *testing.T) {
+		res := NewUncheckedResource(map[string]interface{}{
+			"schema": map[string]interface{}{},
+		})
+		var ages []float64
+		if res.CastColumn("age", &ages) == nil {
+			t.Fatal("want:err got:nil")
+		}
+	})
+	t.Run("HeaderNotFound", func(t *testing.T) {
+		is := is.New(t)
+		res, err := NewResourceFromString(resStr, validator.MustInMemoryRegistry())
+		is.NoErr(err)
+		var ages []float64
+		if res.CastColumn("foo", &ages) == nil {
+			t.Fatal("want:err got:nil")
+		}
+	})
+	t.Run("FieldNotFound", func(t *testing.T) {
+		is := is.New(t)
+		resStr := `
+			{
+				"name":    "col",
+				"data":    "name,age\nfoo,42\nbar,84",
+				"format":  "csv",
+				"profile": "tabular-data-resource",
+				"schema": {"fields": [{"name": "name", "type": "string"},{"name": "Age", "type": "integer"}]}
+			}`
+		res, err := NewResourceFromString(resStr, validator.MustInMemoryRegistry())
+		is.NoErr(err)
+		var ages []float64
+		if res.CastColumn("age", &ages) == nil {
+			t.Fatal("want:err got:nil")
+		}
+	})
+}

datapackage/resource_test.go

@@ -0,0 +1,8 @@
+module github.com/frictionlessdata/datapackage-go
+
+require (
+	github.com/frictionlessdata/tableschema-go v0.1.5-0.20190521014818-f9bf38926664
+	github.com/matryer/is v1.2.0
+	github.com/santhosh-tekuri/jsonschema v1.2.4
+	github.com/satori/go.uuid v1.2.0
+)

go.mod

@@ -0,0 +1,9 @@
+github.com/frictionlessdata/tableschema-go v0.1.5-0.20190521014818-f9bf38926664 h1:IvuZMJ6dH1ye2bWmM8Yla6jj1xIPBR/nZJlm6P4ZSD4=
+github.com/frictionlessdata/tableschema-go v0.1.5-0.20190521014818-f9bf38926664/go.mod h1:OfuE6zbfQdlwx5q9vf5XWXEGJ0LYZcd9ML3zme5rP3k=
+github.com/matryer/is v0.0.0-20170112134659-c0323ceb4e99/go.mod h1:2fLPjFQM9rhQ15aVEtbuwhJinnOqrmgXPNdZsdwlWXA=
+github.com/matryer/is v1.2.0/go.mod h1:2fLPjFQM9rhQ15aVEtbuwhJinnOqrmgXPNdZsdwlWXA=
+github.com/santhosh-tekuri/jsonschema v1.2.4 h1:hNhW8e7t+H1vgY+1QeEQpveR6D4+OwKPXCfD2aieJis=
+github.com/santhosh-tekuri/jsonschema v1.2.4/go.mod h1:TEAUOeZSmIxTTuHatJzrvARHiuO9LYd+cIxzgEHCQI4=
+github.com/satori/go.uuid v1.1.0/go.mod h1:dA0hQrYB0VpLJoorglMZABFdXlWrHn1NEOzdhQKdks0=
+github.com/satori/go.uuid v1.2.0 h1:0uYX9dsZ2yD7q2RtLRtPSdGDWzjeM3TbMJP9utgA0ww=
+github.com/satori/go.uuid v1.2.0/go.mod h1:dA0hQrYB0VpLJoorglMZABFdXlWrHn1NEOzdhQKdks0=