Implement Join to collection

support/collection.go

@@ -5,6 +5,7 @@ import (
     "github.com/spf13/cast"
     "reflect"
 	"strconv"
+    "strings"
 )
 
 type Collection []Value
@@ -209,3 +210,30 @@ func (c Collection) WhereE(key string, operator string, expected interface{}) (C
     }
     return result, err
 }
+
+// Join concatenates the elements of its first argument to create a single string. The separator
+// string sep is placed between elements in the resulting string.
+func (c Collection) Join(key string, sep string) string {
+    result, err := c.JoinE(key, sep)
+    if err != nil {
+        panic(err)
+    }
+    return result
+}
+
+// JoinE concatenates the elements of its first argument to create a single string. The separator
+// string sep is placed between elements in the resulting string.
+func (c Collection) JoinE(key string, sep string) (string, error) {
+    parts := []string{}
+    for _, value := range c {
+        part, err := value.Get(key).StringE()
+        if err != nil {
+            return "", err
+        }
+        parts = append(parts, part)
+    }
+
+    result := strings.Join(parts, sep)
+
+    return result, nil
+}

support/test/collection_test.go

@@ -232,4 +232,32 @@ func Test_collection_where_slice_has_other_integer(t *testing.T) {
 	require.Equal(t, 1, len(result))
 }
 
+func Test_collection_join_one(t *testing.T) {
+	data := support.NewCollection([]map[string]interface{}{
+		{
+			"id": 32,
+		},
+	},
+	)
+
+	result := data.Join("id", ", ")
+
+	require.Equal(t, "32", result)
+}
+
+func Test_collection_join_multiple(t *testing.T) {
+    data := support.NewCollection([]map[string]interface{}{
+        {
+            "id": 32,
+            },
+            {
+            "id": 43,
+            },
+            })
+
+    result := data.Join("id", ", ")
+
+    require.Equal(t, "32, 43", result)
+}
+
 var emptyInterface interface{}