Someone doesn't understand what i want. I want to know what i can do with a pointer.
I have js cloud code.
I have a pointer.
What can i do with it?
Example:
var query = new Parse.Query("Messages"); //POINTER QUERY
console.log(userMessages[0].get("messageId"));
console.log("end2");
query.equalTo("objectId",userMessages[position].get("messageId"));
In the example, userMessages is the result of a prior cloud query.
This line
console.log(userMessages[0].get("messageId"));
helpfully outputs
{"__type":"Pointer","className":"Messages","objectId":"5J4eOletgz"}
This is less useful than you might imagine. I cannot seem to call the objectId from it, and the query
query.equalTo("objectId",userMessages[position].get("messageId"));
query.find ({ ... });
returns nothing. Note that the query should find the pointer-object the pointer-points-to, but instead it helpfully throws the error
Error: 102 bad special key: __type
Which is just about useless.
What can i do with a pointer?
Why don't the people at parse.com bother to write this stuff up anywhere?
That second question is more like a buddhist koan for them to meditate over, no need to respond!
you can use:
userMessagesQuery.include("messageId")
before you execute your query that returns userMessages and you will get the entire object in "messageId" instead of just a pointer.
Also you use
userMessages[0].get("messageId").fetch({success:function(){}})
to get the full object if you don't want to use "include"
Suggestion: I'd rename "messageId" to "message" to make it clear that it's an object pointer and not an ID field.
A pointer is a Parse object with just the minimal data used for linking. If you want to get the rest of the data for a pointer (fully populate it), use the fetch() method.
If you just want the objectId from a pointer, you retrieve it just like you would any other Parse object, by using the myPointer.objectId property.
In your case the following would work, but isn't the most optimal solution:
// I would suggest renaming messageId if you're actually storing pointers
var messagePointer = userMessages[position].get("messageId");
query.equalTo("objectId", messagePointer.objectId);
Instead, as stated by #RipRyness, you could just change your previous query to include() the full object, avoiding many extra queries.
userMessagesQuery.include("messageId");
// ... later in success handler ...
// now a fully populated Message object
var message = userMessages[position].get("messageId");
console.log(message);
Okay so a pointer is does not only point to a certain object, but it can BE that object.
In the query that returns the userMessages result, you can use the line .include("messageId") - this makes your query not only return a pointer to that object, it actually includes that object in place of the pointer.
After using the include statement, userMessages[0].get("messageId") will return the Message object linked that that userMessage object. You no longer need to query the Message collection to get the object.
Related
What I am really interested in with data-loader is the per request caching. For example say my graphql query needs to call getUser("id1") 3x. I would like something to dedupe that call.
However it seems like with data-loader I need to pass in an array of keys into my batch function, and multiple requests will be batched into one api calls.
This has me making a few assumptions that i dont like:
1.) That each service I am calling has a batch api (some of the ones im dealing with do not).
2.) What if multiple calls get batched into 1 api call, and that call fails because 1 of the items was not found. Normally I could handle this by returning null for that field, and that could be a valid case. Now however my entire call may fail, if the batch API decides to throw an error since 1 item was not found.
Is there anyway to use dataloader with single-key requests.
Both assumptions are wrong because the implementation of the batch function is ultimately left up to you. As indicated in the documentation, the only requirements when writing your batch function are as follows:
A batch loading function accepts an Array of keys, and returns a Promise which resolves to an Array of values or Error instances.
So there's no need for the underlying data source to also accept an array of IDs. And there's no need for one or more failed calls to cause the whole function to throw since you can return either null or an error instance for any particular ID in the array you return. In fact, your batch function should never throw and instead should always return an array of one or more errors.
In other words, your implementation of the batch function might look something like:
async function batchFn (ids) {
const result = await Promise.all(ids.map(async (id) => {
try {
const foo = await getFooById(id)
return foo
} catch (e) {
// either return null or the error
}
}))
}
It's worth noting that it's also possible to set the maxBatchSize to 1 to effectively disable batching. However, this doesn't change the requirements for how your batch function is implemented -- it always needs to take an array of IDs and always needs to return an array of values/errors of the same length as the array of IDs.
Daniel's solution is perfectly fine and is in fact what I've used so far, after extracting it into a helper function.
But I just found another solution that does not require that much boilerplate code.
new DataLoader<string, string>(async ([key]) => [await getEntityById(key)], {batch: false});
When we set batch: false then we should always get a key-array of size one passed as argument. We can therefore simply destructure it and return a one-sized array with the data. Notice the brackets arround the return value! If you omit those, this could go horribly wrong e.g. for string values.
I have a SecTrustRef object from the system that I'd like to evaluate myself. Just calling SecTrustEvaluateAsync will be sufficient for this job. The problem is, I must evaluate it in a different process as only this other process has access to the keychains where the CA certificates are stored that may cause evaluation to succeed.
The two processes have an IPC link that allows me to exchange arbitrary byte data between them but I don't see any way to easily serialize a SecTrustRef into byte data and deserialize that data back to an object at the other process. There doesn't seem to be a persistent storage mechanism for SecTrustRef.
So am I overlooking something important here, or do I really have to get all the certs (SecTrustGetCertificateAtIndex) and all the policies (SecTrustCopyPolicies) and serialize these myself?
And if so, how would I serialize a policy?
For the certificate (SecCertificateRef) it's rather easy, I just call SecCertificateCopyData and later on SecCertificateCreateWithData.
But for policies I can only call SecPolicyCopyProperties on one side and later on SecPolicyCreateWithProperties, however the later one requires a 2nd parameter, a policyIdentifier and I see no way to get that value from an existing policy. What am I missing?
Reading through the source of the Security framework, I finally figured it out how to copy a SecPolicyRef:
SecPolicyCreateWithProperties wants what it calls a "policyIdentifier". It's a constant like kSecPolicyAppleIPsec.
This does not get stored directly by the function, it's comparing the value and calling dedicated internal "initializers" (like SecPolicyCreateIPsec).
These in turn call SecPolicyCreate (which is private). They end up passing the same identifier value that you passed to SecPolicyCreateWithProperties.
And this value then gets stored as-is in the _oid field!
The identifier is actually the OID. You can get it either via SecPolicyCopyProperties(policy) (stored in the dictionary with key kSecPolicyOid) or via SecPolicyGetOID (but that returns it as an inconvenient CSSM_OID). Some of those specialized initializers also use values from the properties dictionary passed to SecPolicyCreateWithProperties, those should be present in the copied properties dictionary already.
So this gives us:
Serialization:
CFDictionaryRef createSerializedPolicy(SecPolicyRef policy) {
// Already contains all the information needed.
return SecPolicyCopyProperties(policy);
}
Deserialization:
SecPolicyRef createDeserializedPolicy (CFDictionaryRef serialized) {
CFStringRef oid = CFDictionaryGetValue(serialized, kSecPolicyOid);
if (oid == NULL || CFGetTypeID(oid) != CFStringGetTypeID()) {
return NULL;
}
return SecPolicyCreateWithProperties(oid, serialized);
}
To reproduce the original SecTrustRef as closely as possible, the anchors need to be copied as well. There is an internal variable _anchorsOnly which is set to true once you set anchors. Unfortunately, there is no way to query this value and I've seen it being false in trusts passed by NSURLSession, for example. No idea yet on how to get this value in a public way.
Another problematic bit are the exceptions: if _exceptions is NULL but you query them via SecTrustCopyExceptions(trust), you do get data! And if you assign that to the deserialized trust via SecTrustSetExceptions(trust, exceptions) you suddenly end up with exceptions that were not there before and can change the evaluation result! (I've seen those suddenly appearing exceptions lead to an evaluation result of "proceed" instead of "recoverable trust failure").
I'm working with socket.io. I am having trouble receiving data from the server even though I can console.log() the data (an array of objects) right before I try to emit the data back to the calling client. If I hard code info into the emit, it will display on the client but when I use the dynamically created array of objects, it doesn't go through. My gut tells me its a asyn issue but I'm using bluebird to manage that. Perhaps its an encoding issue? I tried JSON.stringify and JSON.parse, no dice.
Server
socket.on('getClassList', function(){
sCon.getClassList()
.then(function(data){
console.log(data) //data is an array full of objects
socket.emit('STC_gotDatList', data)
})
})
Hard-Coded Expected Output:
classes['moof'] = {
accessList: [888],
connectedList: [],
firstName: "sallyburnsjellyworth"
}
Client
socket.on('STC_gotDatList', function(info){
console.log(info) //prints [] or {}
})
EDIT:
I remember reading somewhere that console.log() may not be printing data at the time the data is available/populated. Could that be it even though im using Promises? At the time I'm emitting the data, it just hasn't been populated into the array? How would i troubleshoot this scenario?
EDIT2:
A step closer. In order to get anything to return, for some reason I have to return each specific object in the 'classes' array. It wont allow me to send the entire array, for the example I gave above, to get data to the client, I have to return(classes['moof']), can't return(classes) to get the entire array... Not sure why.
EDIT3: Solution: You just can't do it this way. I had to put 'moof' inside classes as a property (className) and then I was able to pass the whole classes array.
How is the 'classes' array created?
The problem might be that it is being given properties dynamically, but has not been created as an object, but rather an array.
If you plan to dynamically add properties to it (like property moof), you should create it as an object (with {}) rather than an array (with []).
Try
var classes = {};//instead of classes = []
//then fill it however you do it
classes[property] = {
accessList: [888],
connectedList: [],
firstName: "sallyburnsjellyworth"
};
Also, the credit goes to Felix, I'm just paraphrasing his answer: https://stackoverflow.com/a/8865468/7573546
Looking at the Error Handling Programming Guide, I understand that in cases like the following I must never evaluate the NSError parameter theError unless the return value is NO
BOOL success = [myDoc writeToURL:[self docURL] ofType:#"html" error:&theError];
What happens in casses when the return value is not a success BOOL, and instead it is a collection object?
Take for example [NSIncrementalStore obtainPermanentIDsForObjects:error]. I must not evaluate an error using the error parameter. What should I look for? I imagine I could receive either a nil pointer or an empty array. In this case an empty array does not seem a good response, although in other functions an empty array might be a good one. I can read that if an error occurs, the error object will contain a description of what happened, but it is not so clear how can I find out that an error actually happened.
What is the normal Cocoa or Foundation way to indicate an error in cases like these?
For that method, you're expected to return an array of as many items as you had objects passed in. I'd say that if you don't do that (either the array is nil or empty), you're in an error condition, since you're violating what the documentation says will happen:
An array containing the object IDs for the objects in array.
The returned array must return the object IDs in the same order as the objects appear in array
I am using Marshal class to serialize a Ruby object, using the functions: dump() and load() everything works well, but when a value not related to any serialized data is passed, the load() function returns the expected and logical error:
incompatible marshal file format (can't be read)
format version 4.8 required; 45.45 given
What I need is to check if this data had already been serialized or not before loading it. My goal is to avoid this error and do something else.
Ok. I've encountered very similar problem and, based on hints from this post http://lists.danga.com/pipermail/memcached/2007-December/006062.html, I've figured out that this happens when you either try to load data that was not marshaled before or the data was stored improperly (e.g. not in binary field in database).
In my case specifically I used text type instead of binary field in database, and marshal data got mangled.
Changing type of column from text to binary helped. Unfortunately you cannot convert old (corrupted) data, so you have to drop the column and create it again as binary.
Maybe just rescue from the error?
begin
Marshal.load("foobar")
rescue TypeError
# not a marshalled object, do something else
puts "warning: could not load ..."
end
I have applied Padde way, but using a function that does the job for me and get me back the object, either preexistent or new created as following:
def get_serialized_banner
begin
#banner_obj = Marshal.load(self.path)
rescue TypeError
self.path = Marshal.dump(Banner.new())
self.save
#banner_obj = Marshal.load(self.path)
end
return #banner_obj
end