[iOS] Add last page info.

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

@@ -440,6 +440,12 @@ typedef enum : NSUInteger {
  */
 - (void)setViewportWidth:(CGFloat)width;
 
+/**
+ * @abstract Get information about the last rendered page.
+ Useful fot debugging and fixing online bugs.
+ */
++ (NSDictionary*)lastPageInfo;
+
 /** 
  * Deprecated 
  */

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

@@ -60,6 +60,9 @@
 
 NSTimeInterval JSLibInitTime = 0;
 
+static NSString* lastPageInfoLock = @"";
+static NSDictionary* lastPageInfo = nil;
+
 typedef enum : NSUInteger {
     WXLoadTypeNormal,
     WXLoadTypeBack,
@@ -316,6 +319,11 @@ - (void)renderWithURL:(NSURL *)url options:(NSDictionary *)options data:(id)data
         return;
     }
     WXLogInfo(@"pageid: %@ renderWithURL: %@", _instanceId, url.absoluteString);
+
+    @synchronized (lastPageInfoLock) {
+        lastPageInfo = @{@"pageId": [_instanceId copy], @"url": [url absoluteString] ?: @""};
+    }
+
     [WXCoreBridge install];
     if (_useBackupJsThread) {
         [[WXSDKManager bridgeMgr] executeJSTaskQueue];
@@ -339,6 +347,10 @@ - (void)renderView:(id)source options:(NSDictionary *)options data:(id)data
     _options = [options isKindOfClass:[NSDictionary class]] ? options : nil;
     _jsData = data;
     WXLogInfo(@"pageid: %@ renderView pageNmae: %@  options: %@", _instanceId, _pageName, options);
+
+    @synchronized (lastPageInfoLock) {
+        lastPageInfo = @{@"pageId": [_instanceId copy], @"options": options ? [options description] : @""};
+    }
 
     [WXCoreBridge install];
     if (_useBackupJsThread) {
@@ -1141,6 +1153,15 @@ - (void)didDisappear
     }
 }
 
++ (NSDictionary*)lastPageInfo
+{
+    NSDictionary* result;
+    @synchronized (lastPageInfoLock) {
+        result = [lastPageInfo copy];
+    }
+    return result;
+}
+
 @end
 
 @implementation WXSDKInstance (Deprecated)