associated-object | 易学教程

Rails querying an associated models scope

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问题 I am struggling to find a suitable solution for what should be a simple task. Essentially I have a category model which has many posts . The post belongs to the category . I am displaying categories as part of a search form as well as a number of other places and do not want to display categories that have no associated posts. That seems kind of pointless. I managed to solve this problem by adding the following method to my category model. # Check if Category has associated results def self

Accessing extra data in a sqlalchemy associated object

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问题 The User object can be involved with a Project in many different ways, specified by Job association table. In my template file, I'm trying to loop through all of the projects in current_user.projects and with each one, specify what the Job was for that user in that project... but I can't get the syntax right. MODELS class Project(db.Model): id = db.Column(db.Integer(), primary_key=True) title = db.Column(db.String(80)) users = db.relationship("Job", back_populates="project") class User(db

Accessing extra data in a sqlalchemy associated object

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Accessing extra data in a sqlalchemy associated object

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Swift - Associated value or extension for an Enum

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问题 General question regarding swift enum. I want to create an enum of "icon" and "associate" a value to the enum case enum Icon { case plane case arrow case logo case flag } I want to create an associated image to the enum's value. And also an associated color to the enum value So for instance if it was possible to do something like: extension Icon.plane { var image = { get { return UIImage("plane.png") } } var color = { get { return UIColor.greenColor() } } } var image = Icon.arrow.image // the

How can I declare a private property within a named category?

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问题 I know about the possibility of declaring private properties on a class by putting them inside an unnamed category on that class declared in the implementation ( .m ) file of that class. That's not what I want to do. I'm dealing with a named category on a class that adds some functionality to that class. For this functionality, it would help me very much to have a private property to use in my category - so the usual way of achieving this (described above) doesn't seem to work for me. Or does

Getting id of associated child records in factory_boy

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问题 I have a function with a number of parameters , then a specialized instantiation of that function, with some settings for each of the function's parameters. So I have a structure like the following: class Function(models.Model): name = models.CharField() class FunctionParameter(models.Model): function = models.ForeignKey(Function) class FunctionInstantiation(models.Model): function = models.ForeignKey(Function) class ParameterSetting(models.Model): function_instantiation = models.ForeignKey

How can I declare a private property within a named category?

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I know about the possibility of declaring private properties on a class by putting them inside an unnamed category on that class declared in the implementation ( .m ) file of that class. That's not what I want to do. I'm dealing with a named category on a class that adds some functionality to that class. For this functionality, it would help me very much to have a private property to use in my category - so the usual way of achieving this (described above) doesn't seem to work for me. Or does it? Please enlighten me! Inside your category's implementation file, declare another category and call

Avoid extra static variables for associated objects keys

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When using associated objects, an Objective-C runtime feature available starting from iOS 4 and OSX 10.6, it's necessary to define a key for storing and retrieving the object at runtime. The typical usage is defining the key like follows static char const * const ObjectTagKey = "ObjectTag"; and then use is to store the object objc_setAssociatedObject(self, ObjectTagKey, newObjectTag, OBJC_ASSOCIATION_RETAIN_NONATOMIC); and retrieve it objc_getAssociatedObject(self, ObjectTagKey); (example taken by http://oleb.net/blog/2011/05/faking-ivars-in-objc-categories-with-associative-references/ ) Is

Avoid extra static variables for associated objects keys

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问题 When using associated objects, an Objective-C runtime feature available starting from iOS 4 and OSX 10.6, it's necessary to define a key for storing and retrieving the object at runtime. The typical usage is defining the key like follows static char const * const ObjectTagKey = "ObjectTag"; and then use is to store the object objc_setAssociatedObject(self, ObjectTagKey, newObjectTag, OBJC_ASSOCIATION_RETAIN_NONATOMIC); and retrieve it objc_getAssociatedObject(self, ObjectTagKey); (example