Blendshape at maya

    objExists pCube2   
    objExists |pCube2   
    objExists pCube2|pCubeShape2    
    objExists pCubeShape2   
    objExists |pCubeShape2      

    objExists blendShape1.pCube2x;   
    // Results: 1 //   

    blendShape -q -g blendShape1;
    // Result: pCubeShape1 //  the source shape's name, not transform node's name.
    blendShape -q -target blendShape1;   
    // Result: pCube2 pCube3 // the target shape ‘s transform node’s name.
    blendShape -q -t blendShape1;
    // Result: pCube2 pCube3 // the flag -target is the same as -t
    blendShape –q –weightCount blendShape1;   
    // Result: 2 //            这里返回的数字应该就是刚好上面targets数目
    blendShape -q -w blendShape1;
    // Result: 0.5 0 //  每一个target weight's value. 

    listAttr -sn blendShape1.weight[0];    
    // Result: pCube2x //  这命令可以访问到被Delete而baked的target. 
    listAttr -m blendShape1.w;  
    // Result: pCube2x pCube3 // names of target weight, not the name of target shape or transform node.
    // 这输出也会包含被Delete而baked的targets. 

    getAttr blendShape1.weight;
    // Result: 0.4 0 0.2 //例如(s:pCube1, t:pCube2, pCube3, pCube4), 然后直接按键“Delete"掉pCube3 (pCube3变成baked的了. 

    aliasAttr -q blendShape1;   
    // Result: pCube2x weight[0] pCube3 weight[1] // 对应关系 
    aliasAttr -q blendShape1.pCube2x;   
    // Result: pCube2x //    
    aliasAttr smile blendShape1.weight[0];
    aliasAttr smile blendShape1.w[0]; // weight[0] == w[0] 
    // Result: 1 //  把weight[0]改名为smile, 而不是上面的pCube2x了. 
    aliasAttr -rm blendShape1.smile
    // 会改成weight[x]这个名字 我相信这个x就是target/weight/slider的index. 

    setAttr blendShape1.pCube2x 0.5;  //成功, 调target weight slider的value.   
    setAttr "blendShape1.pCube2x" 0.8; //成功, 调target weight slider的value.   
    setAttr blendShape1.smile 0.6; // Succeed, 
    setAttr blendShape1.w[0] 0.7;  // Succeed, w[0] == weight[0] has been renamed as smile. 

    listConnections blendShape1.it; //一样的
    listConnections blendShape1.inputTarget;
    // Result: 列出所有target shapes (不包括baked)

MString command = "objExists pCube1";
int result = 0; // false;
MStatus status = MGlobal::executeCommand(command, result);

    // mel commands
    blendShape -q -wc blendShapeName; // return the weight count (including the baked&deleted target);
    blendShape -q -t blendShapeName; // retrun the target shpae 's name (no baked&deleted target(
    listAttr -m blendShapeName.w; // return all the names of weights, including the removed or baked&deleted one.
    aliasAttr -q blendShapeName; // return all the weights' names and associated weight[i] 

    // c++ code
    unsigned int iWeightCount = MFnBlendShapeDeformer::numWeights(); 
    MFnBlendShapeDeformer::weightIndexList( MIntArray &indexList );
    assert( iWeightCount == indexList.length() );

    MPlug plugs = blendShapeNode.findPlug("weight", &status); 
    assert( iWeightCount == plugs.numElements() ); // one weight <-> one "weight" plug
    // 这个不一定成立的 例如上面pCube3被remove target了 or 直接按键“Delete”了. 

    for (unsigned int i = 0; i < iWeightCount; ++i)
    {
        MPlug weightPlug = plugs[i]; // we can get the slider/weight name.

        // indexList[] is only a small set of the indices of a very large weight array[],
        // some items of the big weight array[] are not used, some items are
        // deleted and invalid if some targets are removed from weight.
        const int iWeightIndexOfWeightArray = indexList[i]; 
        // this iWeightIndexOfWeightArray can be used to get the weight value and targets.
        ...

        // btw, one weightPlug / slider / weight <--> one FbxBlendShapeChannel
        // the target shapes of this channel become some objects of FbxShape.
    } 

    setAttr "blendshape1.weight1" 0.5

    weightPlug.setDouble( 0.5 ); // MPlug weightPlug; weightPlug.name() == "blendshape1.wieght1"; 

    // given MFnDependencyNode blendShapeNode, and MStatus status;
    MPlug plugs = blendShapeNode.findPlug("weight", &status); 
    for (unsigned int i = 0; i < plugs.numElements(); ++i)
    {
        MPlug weightPlug = plugs[i]; // as destination plug for connection.
        MPlugArray inPlug; // as source plug for connection.
        weightPlug.connectedTo(inPlug, true, false);
        for (unsigned int i = 0; i < inPlug.length(); ++i)
            MGlobal::displayInfo(inPlug[i].name() + " + " + weightPlug.name()); // for debug.   
    }

    // mel command below: 
    listAttr -m blendShape1.w;
    // for example returns weight1 weight2 ... 
    connectionInfo -sourceFromDestination blendShape1.weight1;
    // for example returns pPlane1.translateX, the source of the connection (string, empty if null).
    connectionInfo -destinationFromSource pPlane1.translateX;
    // for example returns blendShape1.weight1 

    // target shape is removed from this blendshape for some reason.
    // target shape is re-added into the blendshape. we want to 
    // restore those connections before. how to do this?
    MString commandString = "connectAttr " + inPlug[i].name() + " " + weightPlug.name();
    MGlobal::executeCommand(commandString, true); // true: display the result.