* [ios] ensure default modules/components/handlers are ready before create instance.

Author: cxfeng1

ios/sdk/WeexSDK/Sources/Engine/WXSDKEngine.h

@@ -13,7 +13,12 @@
 @interface WXSDKEngine : NSObject
 
 /**
- *  @abstract Registers a module for a given name
+ *  @abstract Register default modules/components/handlers, they will be reigstered only once.
+ **/
++ (void)registerDefaults;
+
+/**
+ *  @abstract Register a module for a given name
  *
  *  @param name The module name to register
  *

ios/sdk/WeexSDK/Sources/Engine/WXSDKEngine.m

@@ -208,13 +208,21 @@ + (void)initSDKEnvironment:(NSString *)script
         return;
     }
 
-    [self _registerDefaultComponents];
-    [self _registerDefaultModules];
-    [self _registerDefaultHandlers];
+    [self registerDefaults];
 
     [[WXSDKManager bridgeMgr] executeJsFramework:script];
 }
 
++ (void)registerDefaults
+{
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        [self _registerDefaultComponents];
+        [self _registerDefaultModules];
+        [self _registerDefaultHandlers];
+    });
+}
+
 + (NSString*)SDKEngineVersion
 {
     return WX_SDK_VERSION;

ios/sdk/WeexSDK/Sources/Model/WXSDKInstance.m

@@ -25,6 +25,7 @@
 #import "WXResourceRequest.h"
 #import "WXResourceResponse.h"
 #import "WXResourceLoader.h"
+#import "WXSDKEngine.h"
 
 NSString *const bundleUrlOptionKey = @"bundleUrl";
 
@@ -173,6 +174,9 @@ - (void)_renderWithMainBundleString:(NSString *)mainBundleString
         }
     });
 
+    // ensure default modules/components/handlers are ready before create instance
+    [WXSDKEngine registerDefaults];
+    
     [[WXSDKManager bridgeMgr] createInstance:self.instanceId template:mainBundleString options:dictionary data:_jsData];
 
     WX_MONITOR_PERF_SET(WXPTBundleSize, [mainBundleString lengthOfBytesUsingEncoding:NSUTF8StringEncoding], self);