SHUNMIAN

1 Interface and API Design
2 Reference

1 Interface and API Design

Item 15：Use Prefix Names to Avoid Namespace Clashes

Since Objective-C dosen’t have namespace like other language such as Java's Package and Python's Module，Prefix is the solution that minimize name clash possibility.

Choose 3 letter prefix(from your company & application) for your class. Apple reserve the 2 letter prefix for its future use.
If your own library use a thrid-party library, be sure to prefix the thrid-party library as well. For example, your library has LALClient, if the thrid-party library has prefixed class as XYZData, you’d better to reprefix XYZData as LALXYZData. By doing so, if other people install your library and also XYZData, there would be no clash; it also allow other people to install a different version of XYZData。This convention is common such as in RestKit, which use AFNetworking，it reprefix it as AFRK....

Item 16：Have a Designated Initializer

Designated Initializer

Item 17：Implement the description Method

Implement description method to provide a meaningful string description of instances
If the object description could do with more detail for use during debugging (po command for LLDB), implement debugDescription(default to description).

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10 //use dictionary format for description provides compact visualization of object information.
-(NSString *)description{
    return [NSString stringWithFormat:@"<%@:%p,%@>",
        [self class],
        self,
        @{@"title": _title,
          @"labitude":_labitude,
          @"longitude": _longitude
    }
}

Item 18：Prefer Immutable Objects

When possible, create objects that are immutable (readonly property in .h);
Extend read-only properties in a class-extention to read-write if the property will be set internally.
Provide methods to mutate collections held by objects rather than exposing a mutable collection as a property.

Item 19：Use Clear and Consistent Naming

The conciseness comes at the cost of ambiguity. While Objective-C reach unambiguity via verbosity. The Objective-C code reads like sentences with minimal ambiguity. This is what called self-documenting(自文档), code itself is enough to convery its functionality at most time.

Ensure method names are concise but precise to make them read from left to right as a sentence.
Avoid using abbreviations of types in method names.
Most important, make sure that method names are consistent with your own code or that with which it is being integrated.

Item 20：Prefix Private Method Names

Prefix priavate method names so that they are easily distinguished from public methods.
Avoid using a single underscroe as the method prefix, since this is reserved by Apple.

A better choice is to use double underscore __someMethod instead of p_someMethod.

Item 21：Understand the Objective-C Error Model

Use exceptions only for tatal errors that should bring down the entire application, such as sending message to abstract class.
For nonfatal errors, either provide a delegate method to handle errors or offer an out-parameter NSError object.

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11 //out-parameter NSError object
-(BOOL)doSomething:(NSError **)error{
    //some implementation
}

NSError *error = nil;

BOOL ret = [object doSomething:&error];
if(error){
    // There was an error
}