Added destination scan support for flags

flag.go

@@ -237,9 +237,10 @@ func (f IntSliceFlag) getName() string {
 
 // BoolFlag is a switch that defaults to false
 type BoolFlag struct {
-	Name   string
-	Usage  string
-	EnvVar string
+	Name        string
+	Usage       string
+	EnvVar      string
+	Destination *bool
 }
 
 // String returns a readable representation of this value (for usage defaults)
@@ -264,6 +265,10 @@ func (f BoolFlag) Apply(set *flag.FlagSet) {
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.BoolVar(f.Destination, name, val, f.Usage)
+			return
+		}
 		set.Bool(name, val, f.Usage)
 	})
 }
@@ -312,10 +317,11 @@ func (f BoolTFlag) getName() string {
 
 // StringFlag represents a flag that takes as string value
 type StringFlag struct {
-	Name   string
-	Value  string
-	Usage  string
-	EnvVar string
+	Name        string
+	Value       string
+	Usage       string
+	EnvVar      string
+	Destination *string
 }
 
 // String returns the usage
@@ -345,6 +351,10 @@ func (f StringFlag) Apply(set *flag.FlagSet) {
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.StringVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
 		set.String(name, f.Value, f.Usage)
 	})
 }
@@ -356,10 +366,11 @@ func (f StringFlag) getName() string {
 // IntFlag is a flag that takes an integer
 // Errors if the value provided cannot be parsed
 type IntFlag struct {
-	Name   string
-	Value  int
-	Usage  string
-	EnvVar string
+	Name        string
+	Value       int
+	Usage       string
+	EnvVar      string
+	Destination *int
 }
 
 // String returns the usage
@@ -383,6 +394,10 @@ func (f IntFlag) Apply(set *flag.FlagSet) {
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.IntVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
 		set.Int(name, f.Value, f.Usage)
 	})
 }
@@ -394,10 +409,11 @@ func (f IntFlag) getName() string {
 // DurationFlag is a flag that takes a duration specified in Go's duration
 // format: https://golang.org/pkg/time/#ParseDuration
 type DurationFlag struct {
-	Name   string
-	Value  time.Duration
-	Usage  string
-	EnvVar string
+	Name        string
+	Value       time.Duration
+	Usage       string
+	EnvVar      string
+	Destination *time.Duration
 }
 
 // String returns a readable representation of this value (for usage defaults)
@@ -421,6 +437,10 @@ func (f DurationFlag) Apply(set *flag.FlagSet) {
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.DurationVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
 		set.Duration(name, f.Value, f.Usage)
 	})
 }
@@ -432,10 +452,11 @@ func (f DurationFlag) getName() string {
 // Float64Flag is a flag that takes an float value
 // Errors if the value provided cannot be parsed
 type Float64Flag struct {
-	Name   string
-	Value  float64
-	Usage  string
-	EnvVar string
+	Name        string
+	Value       float64
+	Usage       string
+	EnvVar      string
+	Destination *float64
 }
 
 // String returns the usage
@@ -458,6 +479,10 @@ func (f Float64Flag) Apply(set *flag.FlagSet) {
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.Float64Var(f.Destination, name, f.Value, f.Usage)
+			return
+		}
 		set.Float64(name, f.Value, f.Usage)
 	})
 }