friendly apis for constructors

p2p/switch.go

@@ -78,7 +78,7 @@ type Switch struct {
 }
 
 // NewSwitch creates a new Switch with the given config.
-func NewSwitch(cfg *config.P2PConfig, metrics *Metrics) *Switch {
+func NewSwitch(cfg *config.P2PConfig, options ...func(*Switch)) *Switch {
 	sw := &Switch{
 		config:       cfg,
 		reactors:     make(map[string]Reactor),
@@ -87,7 +87,7 @@ func NewSwitch(cfg *config.P2PConfig, metrics *Metrics) *Switch {
 		peers:        NewPeerSet(),
 		dialing:      cmn.NewCMap(),
 		reconnecting: cmn.NewCMap(),
-		metrics:      metrics,
+		metrics:      NopMetrics(),
 	}
 
 	// Ensure we have a completely undeterministic PRNG.
@@ -102,9 +102,21 @@ func NewSwitch(cfg *config.P2PConfig, metrics *Metrics) *Switch {
 	sw.mConfig = mConfig
 
 	sw.BaseService = *cmn.NewBaseService(nil, "P2P Switch", sw)
+
+	for _, option := range options {
+		option(sw)
+	}
+
 	return sw
 }
 
+// WithMetrics sets the metrics.
+func WithMetrics(metrics *Metrics) func(*Switch) {
+	return func(sw *Switch) {
+		sw.metrics = metrics
+	}
+}
+
 //---------------------------------------------------------------------
 // Switch setup
 

p2p/test_util.go

@@ -137,7 +137,7 @@ func MakeSwitch(cfg *config.P2PConfig, i int, network, version string, initSwitc
 	nodeKey := &NodeKey{
 		PrivKey: crypto.GenPrivKeyEd25519(),
 	}
-	sw := NewSwitch(cfg, NopMetrics())
+	sw := NewSwitch(cfg)
 	sw.SetLogger(log.TestingLogger())
 	sw = initSwitch(i, sw)
 	ni := NodeInfo{