Re: Mutator chaining considered harmful

Chained mutators can

Save typing
Create symmetry
Result in clearer code.

Here's a snippet from my own code. This probes a real-time audio application with a five channel OpenGL oscilloscope:

  my $s= Scope->new('probe' => $netlist)
            ->anatrace('in', 'System input', 'active', 1)
            ->anatrace('out_1', 'Lpf bank1', 'active', 1)
            ->anatrace('out_2', 'Lpf bank2', 'active', 1024)
            ->anatrace('out', 'System output', 'active', 1)
            ->anatrace('bank2', 'Switch pos', 'active', 1)
            ->generate();
[download]

Want to see another channel? Call anatrace again.

I don't think that features with potential downsides should be 'considered harmful'.

It is possible to create a 'little language' out of chained method calls. I avoid creating little languages because I have seen a few of them grow into voracious blood-sucking monsters. I can enjoy chaining method calls without fear of triggering a science-related memetic disorder.

It should work perfectly the first time! - toma

Comment on Re: Mutator chaining considered harmful Download Code

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Re^2: Mutator chaining considered harmful by kappa (Chaplain) on Dec 29, 2004 at 14:11 UTC
This gives you almost nothing in comparison with: `... $s->anatrace('bank2', 'Switch pos', 'active', 1); $s->generate();` [download] And when the objects have long names or are expressions you can always: `for (Scope->new('probe' => $netlist)) { $_->anatrace('in', 'System input', 'active', 1); ... $_->generate(); }` [download] --kap	[reply] [d/l] [select]
Re^2: Mutator chaining considered harmful by Aristotle (Chancellor) on Dec 29, 2004 at 19:39 UTC
Apart from kappa's points: read my root node update. Here's what that would look like with a good interface: `my $s = Scope->new( 'probe' => $netlist ); $s->anatrace( in => [ 'System input', 'active', 1 ], out_1 => [ 'Lpf bank1', 'active', 1 ], out_2 => [ 'Lpf bank2', 'active', 1024 ], out => [ 'System output', 'active', 1 ], bank2 => [ 'Switch pos', 'active', 1 ], ); $s->generate();` [download] Makeshifts last the longest.	[reply] [d/l]
Re^3: Mutator chaining considered harmful by toma (Vicar) on Dec 29, 2004 at 21:29 UTC
I suppose I could also use this :-) `my $s = Scope->new( probe => $netlist ) ->anatrace( in => [ 'System input', 'active', 1 ], out_1 => [ 'Lpf bank1', 'active', 1 ], out_2 => [ 'Lpf bank2', 'active', 1024 ], out => [ 'System output', 'active', 1 ], bank2 => [ 'Switch pos', 'active', 1 ], ) ->generate();` [download] The `=>` after the first arguments look nice, especially since the first arguments are instance handles, and I use them as a hash key. In this example the arguments to anatrace really aren't mutators, they are constructors of sub-objects. They are waveforms being added to a scope display. update Is the problem that you perceive just with mutators, or does it also apply to sub-object constructors? Can you provide examples of acceptable method chaining, and contrast it with problematic method chaining? It should work perfectly the first time! - toma	[reply] [d/l]


Think about Loose Coupling
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