NSApplication - AppKit | Apple Developer Documentation
An NSApplication object has a delegate (an object that you assign) that is notified The main() function Xcode creates begins by calling a function named . a given mask, or nil if no such event is found before a specified expiration date. calendar:didSelectDate delegate method is sending a wrong date to method # Tested in an iPhone 7 simulator, ran through xcode . After this call my date is reverted back to the 19th at 21h (even the offset is Because I don't know all the ins and outs of FSCalendar I'm not so sure on how to fix. A return type of a method is not part of the signature of the method for the of the method when determining the compatibility between a delegate and the . Therefore, changes to the object in the called method have no effect on the Dates and Times Summary · Declarations and Constants Summary.
Optional modifiers such as abstract or sealed. The return value, or void if the method has none.
Method parameters are enclosed in parentheses and are separated by commas. Empty parentheses indicate that the method requires no parameters. These parts together form the method signature. Note A return type of a method is not part of the signature of the method for the purposes of method overloading. However, it is part of the signature of the method when determining the compatibility between a delegate and the method that it points to.
The following example defines a class named Motorcycle that contains five methods: Two methods have the same name, but must be differentiated by their parameter types. Method invocation Methods can be either instance or static. Invoking an instance method requires that you instantiate an object and call the method on that object; an instance method operates on that instance and its data.
You invoke a static method by referencing the name of the type to which the method belongs; static methods operate do not operate on instance data. Attempting to call a static method through an object instance generates a compiler error.
Creating and Using Your Own Delegates in Objective-C
Calling a method is like accessing a field. After the object name if you are calling an instance method or the type name if you are calling a static methodadd a period, the name of the method, and parentheses. Arguments are listed within the parentheses, and are separated by commas. The method definition specifies the names and types of any parameters that are required. When a caller invokes the method, it provides concrete values, called arguments, for each parameter.
The arguments must be compatible with the parameter type, but the argument name, if one is used in the calling code, does not have to be the same as the parameter named defined in the method. In the following example, the Square method includes a single parameter of type int named i.
The first method call passes the Square method a variable of type int named num; the second, a numeric constant; and the third, an expression. The methods of the Motorcycle class can therefore be called as in the following example. The call to the Drive method, for example, includes two arguments that correspond to the two parameters in the method's syntax.
The first becomes the value of the miles parameter, the second the value of the speed parameter. AddGas 15 ; moto. When using named arguments, you specify the parameter name followed by a colon ": Arguments to the method can appear in any order, as long as all required arguments are present.
The following example uses named arguments to invoke the TestMotorcycle. In this example, the named arguments are passed in the opposite order from the method's parameter list.
However, a positional argument cannot follow a named argument. The following example invokes the TestMotorcycle. Drive method from the previous example using one positional argument and one named argument. Since all types in the managed type system inherit directly or indirectly from the Object class, all types inherit its members, such as Equals ObjectGetTypeand ToString.
The following example defines a Person class, instantiates two Person objects, and calls the Person.
Equals method to determine whether the two objects are equal. The Equals method, however, is not defined in the Person class; it is inherited from Object. False Types can override inherited members by using the override keyword and providing an implementation for the overridden method. The method signature must be the same as that of the overridden method. The following example is like the previous one, except that it overrides the Equals Object method. It also overrides the GetHashCode method, since the two methods are intended to provide consistent results.
True Passing parameters Types in C are either value types or reference types. For a list of built-in value types, see Types and variables.
By default, both value types and reference types are passed to a method by value. Passing parameters by value When a value type is passed to a method by value, a copy of the object instead of the object itself is passed to the method. Therefore, changes to the object in the called method have no effect on the original object when control returns to the caller. The following example passes a value type to a method by value, and the called method attempts to change the value type's value.
It defines a variable of type int, which is a value type, initializes its value to 20, and passes it to a method named ModifyValue that changes the variable's value to When the method returns, however, the variable's value remains unchanged. That is, the method receives not the object itself, but an argument that indicates the location of the object.
If you change a member of the object by using this reference, the change is reflected in the object when control returns to the calling method. However, replacing the object passed to the method has no effect on the original object when control returns to the caller. The following example defines a class which is a reference type named SampleRefType. It instantiates a SampleRefType object, assigns 44 to its value field, and passes the object to the ModifyObject method.
This example does essentially the same thing as the previous example -- it passes an argument by value to a method. But because a reference type is used, the result is different.
The modification that is made in ModifyObject to the obj. To pass a parameter by reference, you use the ref or out keyword.
You can also pass a value by reference to avoid copying but still prevent modifications using the in keyword. The following example is identical to the previous one, except the value is passed by reference to the ModifyValue method. When the value of the parameter is modified in the ModifyValue method, the change in value is reflected when control returns to the caller.
You pass two variables to a method by reference, and the method swaps their contents. The following example swaps integer values.
Parameter arrays Sometimes, the requirement that you specify the exact number of arguments to your method is restrictive.
- Basic debugging using logging for Swift and Objective-C apps.
By using the params keyword to indicate that a parameter is a parameter array, you allow your method to be called with a variable number of arguments. The parameter tagged with the params keyword must be an array type, and it must be the last parameter in the method's parameter list. A caller can then invoke the method in either of three ways: By passing an array of the appropriate type that contains the desired number of elements. By passing a comma-separated list of individual arguments of the appropriate type to the method.
By not providing an argument to the parameter array. The following example defines a method named DoStringOperation that performs the string operation specified by its first parameter, a StringOperation enumeration member. The strings upon which it is to perform the operation are defined by a parameter array. The Main method illustrates all three ways of invoking the method. Note that the method tagged with the params keyword must be prepared to handle the case in which no argument is supplied for the parameter array, so that its value is null.
Length, arr ; Change ref arr ; Console.
ios - Delegate method in second ViewController not called - Stack Overflow
Debugging Deployed iOS Apps. Simple example Here is an example showing how to call NSLog: The quick brown fox jumps over a lazy dog! Advanced details The definition for the NSLog function appears as follows: If care and attention is not taken to ensure that the contents of the format string match up with the remaining arguments, your app may crash or, at the very least, it will output unusable data to the console.
Back to Top Good things to include in your logs Logging allows you to create a transcript describing the operation of your application that you can later analyze at your leisure. As such, you want to include as much useful information in your logs as possible so that it is easier for you to really see what is happening as your app runs. Here are some items that are commonly included in logs with some explanation: Logic and branching Adding logging statements inside of the logic of your code will help you understand which parts are being executed and which branches in your logic are being utilized.
It is often useful to add many NSLog statements to especially complex sequences of code so you can better understand the flow of execution at runtime. Unique and easy to find text patterns In every log statement, it is useful to include some unique and easy to find text pattern so if you do identify a problem in that log statement you can easily search through your source files and find its location.
Variable and property values Printing variable and property values at key places during the execution of your app will allow you to verify that those values are within acceptable bounds. Printing error messages in your logs that explicitly tell you when values are out of range will help you recognize these cases. This will allow you to display many different kinds of values.
As a convenience, you can use Objective-C's boxing capability to save time and avoid compiler warnings. For example, the following: Who is being called? In analyzing the operation of your application, it may be critical for you to know the sequence in which calls are being made to functions or methods in your application. In these cases, it is a really good idea to add an NSLog statement near the beginning of your method and function definitions that simply prints out the name of the function: